#17 Main Street Capital Corporation MAIN ST CAPITAL CORPORATION Investor Presentation First Quarter - 2023 NYSE: MAIN mainstcapital.com#2Disclaimers Main Street Capital Corporation (MAIN) cautions that statements in this presentation that are forward-looking, and provide other than historical information, involve risks and uncertainties that may impact our future results of operations. The forward-looking statements in this presentation are based on current conditions as of May 5, 2023, and include, but are not limited to, statements regarding our goals, beliefs, strategies, future operating results and cash flows, operating expenses, investment originations and performance, available capital, payment and the tax attributes of future dividends and shareholder returns. Although our management believes that the expectations reflected in any forward-looking statements are reasonable, we can give no assurance that those expectations will prove to have been correct. Those statements are made based on various underlying assumptions and are subject to numerous uncertainties and risks, including, without limitation: our continued effectiveness in raising, investing and managing capital; adverse changes in the economy generally or in the industries in which our portfolio companies operate; the impacts of macroeconomic factors on MAIN and its portfolio companies' business and operations, liquidity and access to capital, and on the U.S. and global economies, including impacts related to the COVID-19 pandemic and other public health crises, risk of recession, inflation, supply chain constraints or disruptions and rising interest rates; changes in laws and regulations or business, political and/or regulatory conditions that may adversely impact our operations or the operations of our portfolio companies; the operating and financial performance of our portfolio companies and their access to capital; retention of key investment personnel; competitive factors; and such other factors described under the captions "Cautionary Statement Concerning Forward-Looking Statements," "Management's Discussion and Analysis of Financial Condition and Results of Operations" and "Risk Factors" included in our filings with the Securities and Exchange Commission (www.sec.gov), including our most recent annual report on Form 10-K and subsequently filed quarterly reports on Form 10-Q. We undertake no obligation to update the information contained herein to reflect subsequently occurring events or circumstances, except as required by applicable securities laws and regulations. Main Street Capital Corporation MAIN ST CAPITAL CORPORATION MAIN has filed a registration statement (which includes a prospectus) with the SEC for any offering to which this communication may relate and may file one or more supplements to the prospectus in the future. Before you invest in any of MAIN's securities, you should read the registration statement, the prospectus and the applicable prospectus supplement(s) in order to fully understand all of the implications and risks of an offering of MAIN's securities. You should also read other documents MAIN has filed with the SEC for more complete information about MAIN and its securities offerings. You may access these documents for free by visiting EDGAR on the SEC website at www.sec.gov. Alternatively, MAIN will arrange to send you any applicable prospectus and prospectus supplement if you request such materials by calling us at (713) 350-6000. These materials are also made available, free of charge, on our website at www.mainstcapital.com. Information contained on our website is not incorporated by reference into this communication. NYSE: MAIN The summary descriptions and other information included herein are intended only for informational purposes and convenient reference. The information contained herein is not intended to provide, and should not be relied upon for, or accounting, legal tax advice or investment recommendations. Before making an investment decision with respect to MAIN, investors are advised consult with their tax, financial, investment and legal advisors. mainstcapital.com Page 2#3Main Street Capital Corporation Corporate Overview and Investment Strategy Main Street Capital Corporation MAIN ST 1st Quarter 2023 NYSE: MAIN CAPITAL CORPORATION | mainstcapital.com Page 3#4MAIN is a Principal Investor in Private Debt and Equity Focus on unique Lower Middle Market debt and equity investment strategy, Asset Management Business and internally managed operating structure differentiates MAIN from other investment firms ● Internally-managed Business Development Company (BDC) IPO in 2007 ● ● Approximately $6.6 billion in capital under management(¹) Approximately $5.0 billion internally at MAIN(¹) Over $1.6 billion as the investment adviser to external parties(¹) Primarily invests in the under-served Lower Middle Market (LMM) ● - ● MAINST CAPITAL CORPORATION Proprietary debt investments in privately held companies typically owned by private equity sponsors (Private Loans) Originated directly by MAIN or through strategic relationships with other investment funds First lien, senior secured debt investments Companies consistent with size of the companies in MAIN's LMM and Middle Market investment strategies Targets companies with revenue between $10 million - $150 million; EBITDA between $3 million $20 million Provides single source solutions, including a combination of first lien, senior secured debt and equity financing Debt investments in Middle Market companies First lien, senior secured and/or rated debt investments Larger companies than LMM investment strategy Attractive asset management advisory business Significant management ownership / investment in MAIN Headquartered in Houston, Texas (1) Capital under management includes undrawn portion of debt capital as of March 31, 2023 Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 4#5MAIN is a Principal Investor in Private Debt and Equity MAIN's unique investment strategy, efficient operating structure and conservative capitalization are designed to provide sustainable, long-term growth in recurring monthly dividends and long-term capital appreciation to our shareholders (1) Includes dividends paid or declared as of May 5, 2023 Main Street Capital Corporation Long-term focus on delivering our shareholders sustainable growth in net asset value and recurring dividends per share ● Consistent cash dividend yield - dividends paid monthly MAIN has never decreased its monthly dividend rate 109% increase in monthly dividends from $0.33 per share paid in Q4 2007 to declared dividends of $0.69 per share for Q3 2023 Supplemental dividends, paid or declared in addition to monthly dividends, of $0.60 per share during the last twelve months(¹) ● MAIN ST ● CAPITAL CORPORATION Owns two Small Business Investment Company (SBIC) Funds • Main Street Mezzanine Fund (2002 vintage) and Main Street Capital III (2016 vintage) ● Provides access to 10-year, low cost, fixed rate U.S. government- backed leverage Strong capitalization and liquidity position - stable, long-term debt and significant available liquidity to take advantage of opportunities Favorable opportunities in capital markets through issuer investment grade rating of BBB-/Stable from Standard & Poor's Global Ratings and BBB-/Stable from Fitch Ratings ● • Total SBIC debenture regulatory financing capacity of $350 NYSE: MAIN million, the maximum amount permitted under current U.S. Small Business Administration (SBA) regulations mainstcapital.com Page 5#6MAIN is a Principal Investor in Private Debt and Equity Focus on LMM equity investments and efficient operating structure differentiates MAIN and provides opportunity for significant total returns for our shareholders ● Equity investments in LMM portfolio provide the opportunity to grow net asset value (NAV) per share and generate recurring dividend income and periodic realized gains to support MAIN's dividend growth ● ● ● ● Internally managed operating structure provides significant operating leverage Favorable ratio of total expenses, excluding interest expense, to average total assets of approximately 1.4%(¹) Greater portion of gross portfolio returns are delivered to our ● ● MAINST CAPITAL CORPORATION NAV growth of $14.38 per share (or 112%) since 2007 Cumulative net realized gains from LMM portfolio investments of $119.2 million since MAIN's initial public offering Approximately $4.82 per share in cumulative, pre-tax net unrealized appreciation on LMM portfolio at March 31, 2023 Realized gains provide opportunities for additional returns in excess of net investment income (1) Based upon the trailing twelve month period ended March 31, 2023 Main Street Capital Corporation shareholders Attractive and growing Asset Management Business benefits MAIN's shareholders Significant positive impact to Net Investment Income (NII) Alignment of interests between MAIN management and our shareholders NYSE: MAIN mainstcapital.com Page 6#7MAIN Strategy Produces Differentiated Returns Enhanced Value Proposition - Three Ways to Win are Better Than One ● 1. Sustain and Grow Dividends Efficient operating structure provides operating leverage to grow Distributable Net Investment Income (DNII)(¹), and dividends paid, as investment portfolio and total investment income grow ● ● ● . ● 2. Meaningfully Grow Net Asset Value (NAV) Per Share $12.85 at December 31, 2007 to $27.23 at March 31, 2023 - 112% growth; CAGR of 5.0% Represents incremental economic return to investors beyond dividends MAIN's debt-focused peers (which comprises most BDCs) cannot generate NAV per share growth through the cycles Unrealized appreciation is a good proxy for future dividend growth without the need for additional capital through growing portfolio dividend income and periodic harvesting of realized gains from equity investments Ability to grow NAV per share provides opportunity for MAIN stock share price appreciation and additional shareholder returns ● MAIN ST CAPITAL CORPORATION ● ● 109% increase in monthly dividends from $0.33 per share paid in Q4 2007 to declared dividends of $0.69 per share for Q3 2023 Never decreased regular monthly dividends (including through 2008/2009 recession and 2020/2021 COVID-19 pandemic) Paid or declared $37.56(²) per share in total dividends since October 2007 IPO at $15.00 per share ($32.67 per share in regular dividends and $4.89 per share in supplemental dividends) (²) Multi-faceted investment strategy supports growth of dividends over various cycles and markets 3. Supplement Growth in DNII(¹) with Periodic Realized Gains LMM equity component of investment strategy provides opportunity for meaningful realized gains (analogous to PIK income on debt investments from cash flow perspective, but more tax efficient and without cap on upside) Realized gains validate the quality of MAIN's unrealized appreciation Realized gains can be retained for future reinvestment due to MAIN's unique tax structure or paid to shareholders as dividends NYSE: MAIN (1) See reconciliation of DNII per share to Net Investment Income per share on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (2) Includes dividends paid or declared as of May 5, 2023 Main Street Capital Corporation mainstcapital.com Page 7#8Historical Monthly Dividends, NAV and DNII(¹) Per Share MAIN's unique focus on equity investments in the LMM provides the opportunity for significant NAV per share growth MAIN's efficient operating structure provides significant operating leverage, greater dividends and greater overall returns for our shareholders DNII and Dividends Per Share $1.10 $1.00 $0.90 $0.80 $0.70 $0.60 $0.50 $0.40 $0.30 $0.20 I I I I + I I t 1 I T I 1 I I I 2008 ● Recessionary Period 2009 2010 I I I T 2011 2012 2013 2014 2015 Monthly Dividends 2016 2017 2018 NYSE: MAIN DNII per share 2019 I I 1 MAIN ST 2020 CAPITAL CORPORATION COVID Pandemic Outbreak 2021 -NAV per share 2022 2023 (1) See reconciliation of DNII per share to Net Investment Income per share on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (2) Includes dividends paid or declared as of May 5, 2023 Main Street Capital Corporation $28.00 $26.00 $24.00 $22.00 $20.00 $18.00 $16.00 $14.00 $12.00 $10.00 In addition to the monthly dividends above, $4.89 per share of supplemental dividends have been paid or declared since 2007 IPO(²) Annual return on equity averaging approximately 13.5% from 2010 through the first quarter of 2023 mainstcapital.com NAV Per Share Page 8#9LMM Investment Strategy LMM investment strategy differentiates MAIN from its competitors and provides attractive risk- adjusted returns Main Street Capital Corporation ● Investment Objectives High cash yield from secured debt investments (12.4% weighted- average cash coupon as of March 31, 2023); plus Dividend income, fair value appreciation and periodic capital gains from equity investments ● Investments are structured for (i) protection of capital, (ii) high recurring income and (iii) meaningful capital gain opportunity ● Focus on self-sponsored, "one stop" financing opportunities Partner with business owners, management teams and entrepreneurs Provide highly customized financing solutions • Recapitalization, buyout, growth and acquisition capital ● MAIN ST ● CAPITAL CORPORATION ● Extensive network of grass roots referral sources Strong and growing "Main Street" brand recognition / reputation NYSE: MAIN Investments have low correlation to the broader debt and equity markets and attractive risk-adjusted returns mainstcapital.com Page 9#10LMM Investment Opportunity MAIN targets LMM investments in established, profitable companies Characteristics of LMM provide beneficial risk- reward investment opportunities Large and critical portion of U.S. economy 195,000+ domestic LMM businesses (1) ● MAIN ST LMM is under-served from a capital perspective and less competitive ● CAPITAL CORPORATION Inefficient asset class generates pricing inefficiencies • Typical entry enterprise values between 4.5X- 6.5X EBITDA Typical entry leverage multiples between 2.0X - 4.0X EBITDA to MAIN debt investment Partner relationship with the management teams of our portfolio companies vs a "commoditized vendor of capital" NYSE: MAIN (1) Source: U.S. Census 2017 - U.S. Data Table by Enterprise Receipt Size; 2017 County Business Patterns and 2017 Economic Census; includes Number of Firms with Enterprise Receipt Size between $10,000,000 and $99,999,999 Main Street Capital Corporation mainstcapital.com Page 10#11Private Loan Investment Strategy Private Loan portfolio investments are primarily debt investments in privately held companies which have primarily been originated directly by MAIN or to a lesser extent through strategic relationships with other credit funds on a collaborative basis (often referred to in the debt markets as "club deals" because of the small lender group size) MAIN's Private Loan investments are typically made to a company owned by or being acquired by a private equity sponsor Investment Objectives Access proprietary investments with attractive risk-adjusted return characteristics Generate cash yield to support MAIN monthly dividend ● Investment Characteristics Investments in companies that are consistent with the size of companies in our LMM and Middle Market strategies Proprietary investments originated directly by MAIN or through strategic relationships with other investment funds on a collaborative basis Current Private Loan portfolio companies have weighted-average EBITDA of approximately $38.1 million(¹) ● ● Investments in secured debt investments First lien, senior secured debt investments Floating rate debt investments ● ● MAIN ST CAPITAL CORPORATION ● 8% -12% targeted gross yields ● • Weighted-average effective yield of 12.4% (2) ● Net returns positively impacted by lower overhead requirements and modest use of leverage Floating rate debt investments provide matching with MAIN's floating rate Credit Facilities (³) (1) This calculation excludes two Private an portfolio companies as EBITDA is a meaningful metric for portfolio companies (2) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status NYSE: MAIN (3) Includes MAIN's corporate revolving credit facility (the Corporate Facility) and SPV credit facility (the SPV Facility and together with the Corporate Facility, the Credit Facilities); see additional details on page 42 Main Street Capital Corporation mainstcapital.com Page 11#12Middle Market Debt Investment Strategy MAIN maintains a portfolio of debt investments in Middle Market companies Investment Objective • Generate cash yield to support MAIN monthly dividend ● MAIN ST Investments in secured and/or rated debt investments First lien, senior secured debt investments Floating rate debt investments ● CAPITAL CORPORATION Larger companies than the LMM investment strategy • Current Middle Market portfolio companies have weighted-average EBITDA of approximately $65.4 million ● Large and critical portion of U.S. economy 220,000+ domestic Middle Market businesses (1) More relative liquidity than LMM and Private Loan investments 6% - 10% targeted gross yields • Weighted-average effective yield of 11.8% (2) Net returns positively impacted by lower overhead requirements and modest use of leverage Floating rate debt investments provide matching with MAIN's floating rate Credit Facilities (3) (1) (2) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status (3) Includes MAIN's Credit Facilities as defined on page 11; see additional details on page 42 Main Street Capital Corporation NYSE: MAIN Source: U.S. Census 2017 - U.S. Data Table by Enterprise Receipt Size; 2017 County Business Patterns and 2017 Economic Census; includes Number of Firms with Enterprise Receipt Size between $10,000,000 and $1,000,000,000 mainstcapital.com Page 12#13Asset Management Business MAIN's asset management business represents additional income diversification and the opportunity for greater shareholder returns MAIN's internally managed operating structure provides MAIN's shareholders the benefits of this asset management business Growth of asset management business is increasingly driven by MAIN's Private Loan investment strategy MAIN(¹) is the investment adviser to several third party clients in its Asset Management Business ● MAIN(¹) is the investment adviser to and administrator of MSC Income Fund, Inc. (MSIF), a non-listed BDC ● MAIN¹ provides asset management services, including sourcing, diligence and post-investment monitoring MAIN(¹) receives management fees and incentive fees Base management fee of 1.75% of total assets MAIN ST CAPITAL CORPORATION ● MAIN(¹) is the investment adviser and administrator to a private fund and a separately managed account with the investment strategies for these clients solely focused on MAIN's Private Loan investment strategy - Incentive fees - 20% of net investment income above a hurdle rate and 20% of net realized capital gains Benefits to MAIN No significant increases to MAIN's operating costs to provide services (utilize existing infrastructure and leverage fixed costs and existing investment capabilities) Monetizing the value of MAIN franchise Significant positive impact on MAIN's financial results $8.1 million contribution to net investment income in the first quarter of 2023(²) $22.2 million contribution to net investment income in the year ended December 31, 2022(²) - $103.2 million of cumulative unrealized appreciation as of March 31, 2023 NYSE: MAIN (1) Through MSC Adviser I, LLC (the External Investment Manager), MAIN's wholly-owned unconsolidated subsidiary (2) Contribution to Net Investment Income includes (a) dividend income received by MAIN from the External Investment Manager and (b) operating expenses allocated from MAIN to the External Investment Manager Main Street Capital Corporation mainstcapital.com Page 13#14MAIN Regulatory Framework Highly regulated structure provides significant advantages and protections to our shareholders, including investment transparency, tax efficiency and beneficial leverage Main Street Capital Corporation ● Operates as a Business Development Company Regulated by Securities and Exchange Commission - 1940 Act Publicly-traded, private investment company ● ● Regulated Investment Company (RIC) tax structure Eliminates corporate level income tax Efficient tax structure providing high yield to investors Passes through capital gains to investors ● ● ● Small Business Investment Company (SBIC) subsidiaries Regulated by the SBA Access to low cost, fixed rate, long-term leverage guaranteed by the U.S. government Total SBIC debenture regulatory financing capacity of $350.0 million Total outstanding leverage of $334.0 million through two wholly owned SBIC funds; $16 million of licensed capacity for additional debentures MAIN is a previous SBIC of the Year Award recipient ● MAIN ST ● CAPITAL CORPORATION ● NYSE: MAIN mainstcapital.com Page 14#15MAIN Corporate Structure - Internally Managed "Internally managed" structure means no external management fees or expenses are paid, providing operating leverage to MAIN's business; MAIN targets total operating and administrative costs at or less than 2% of assets Assets: $3.6 billion Credit Facilities: $564 million ($1.2 billion capacity)(1)(2) Notes: $1.1 billion (3 (3) Main Street Mezzanine Fund, LP (2002 vintage SBIC) Main Street Capital Corporation (BDC/RIC) Assets: $286 million SBIC Debt: $159 million outstanding MAIN ST CAPITAL CORPORATION NYSE: MAIN Main Street Capital III, LP (2016 vintage SBIC) Assets: $383 million SBIC Debt: $175 million outstanding (1) Includes MAIN's Credit Facilities as defined on page 11; see additional details on page 42 (2) As of March 31, 2023, MAIN's Credit Facilities had $1.2 billion in total commitments; MAIN's Credit Facilities include accordion features which could increase total commitments up to $1.8 billion (3) Includes $500.0 million of July 2026 Notes, $450.0 million of May 2024 Notes and $150.0 million of December 2025 Notes (100.0 million issued in Q4 2022 and $50.0 million issued in Q1 2023) Main Street Capital Corporation mainstcapital.com Page 15#16MAIN Executive Management Team Dwayne Hyzak (¹)(2) CEO David Magdol(¹)(2) President and CIO (³) Jesse Morris (1) CFO, COO, EVP Jason Beauvais; JD(1) EVP, GC, CCO(4) and Secretary ● ● ● ● ● ● ● Co-founded MAIN; Joined Main Street group in 2002 Vice President in Lazard Freres Investment Banking Division Vice President of McMullen Group (John J. McMullen's Family Office) Co-founded MAIN; Joined Main Street group in 2002; affiliated with Main Street group since 1999 Director of Acquisitions & Integration with Quanta Services (NYSE: PWR) Manager with a Big 5 Accounting Firm's audit and transaction services groups Joined MAIN in 2008 Attorney for Occidental Petroleum Corporation (NYSE: OXY) Associate in the corporate and securities section at Baker Botts LLP MAIN ST Joined MAIN in 2019 Executive Vice President with Quanta Services (NYSE: PWR) Vice President and CFO Foodservice Operations with Sysco Corporation (NYSE: SYY) Manager with a Big 5 Accounting Firm (1) Member of MAIN Executive Committee (2) Member of MAIN Investment Committee; Vince Foster, MAIN's Chairman of the Board, is also a member of MAIN's Investment Committee Chief Investment Officer (3) (4) Chief Compliance Officer Main Street Capital Corporation CAPITAL CORPORATION NYSE: MAIN mainstcapital.com Page 16#17Monthly Dividends Per Share Sustainable Growth Recurring monthly dividend has never been decreased and has grown meaningfully (109%) since IPO (1) Based upon the current annualized monthly dividends declared for the third quarter of 2023, the annual effective yield on MAIN's stock is 6.8% (²) MAIN has also paid or declared $4.89(³) in supplemental dividends since IPO (¹) Cumulative dividends paid or declared, including supplemental dividends, since IPO(1) (at $15.00 per share) through third quarter of 2023 equal $37.56 per share Trailing Twelve Months Monthly Dividends Per Share $2.70 $2.50 $2.30 $2.10 $1.90 $1.70 $1.50 $1.30 $1.10 2008 2009 2010 2011 2012 2013 2014 2015 NYSE: MAIN 2016 Monthly Dividends (3) 2017 2018 (1) Initial Public Offering, or IPO, in October 2007 (2) As of May 3, 2023; based upon the closing market price of $40.62 per share and the annualized most recently declared monthly dividends (3) Based upon dividends which have been paid or declared as of May 5, 2023 Main Street Capital Corporation 2019 MAINST CAPITAL CORPORATION 2020 2021 2022 2023 mainstcapital.com Page 17#18Total Dividends per Share - Significant Incremental Value to Shareholders MAIN's dividend policy includes an expectation for consistent annual growth of its monthly dividends and meaningful coverage of such monthly dividends with recurring Distributable Net Investment Income (DNII) (³) MAIN's dividend policy includes an expectation for meaningful supplemental dividends to the extent DNII(³) significantly exceeds the monthly dividends MAIN's dividend policy is intended to provide MAIN's shareholders significant comfort regarding the recurring nature of MAIN's monthly dividends and visibility to additional significant value through MAIN's supplemental dividends Trailing Twelve Months Total Dividends Per Share $3.30 $3.10 $2.90 $2.70 $2.50 $2.30 $2.10 $1.90 $1.70 $1.50 $1.30 $1.10 2008 2009 2010 2011 2012 2013 2014 2015 (1) 2016 2017 2018 (2) Monthly Dividends ■ Supplemental Dividends 2019 MAIN ST CAPITAL CORPORATION 2020 2021 (2) Includes supplemental dividends which have been declared as of May 5, 2023 (3) See reconciliation of DNII per share to Net Investment Income per share on page 38 and Non-GAAP Information disclosures on page 48 of this presentation Main Street Capital Corporation NYSE: MAIN 2022 2023 (1) Includes dividends which have been paid or declared for payment on or before June 30, 2023; in May 2023 we also declared regular monthly dividends of $0.69 per share for Q3 2023 mainstcapital.com Page 18#19Main Street Capital Corporation Investment Portfolio Main Street Capital Corporation 1st Quarter 2023 NYSE: MAIN MAIN ST - CAPITAL CORPORATION mainstcapital.com Page 19#20Total Investment Portfolio Diversity provides structural protection to investment portfolio, revenue sources, income, cash flows and shareholder dividends Includes complementary LMM debt and equity investments, Private Loan debt investments and Middle Market debt investments Total investment portfolio at fair value consists of approximately 51% LMM/ 36% Private Loan / 7% Middle Market / 6% Other Portfolio(¹) investments ● 195 LMM, Private Loan and Middle Market portfolio companies Average investment size of $18.7 million (²) ● ● ● ● Significant diversification Issuer Industry Transaction type ● ● MAIN ST (3) Largest individual portfolio company represents 3.7% of total investment income and 3.1% of total portfolio fair value (most investments are less than 1% of income and fair value) CAPITAL CORPORATION 13 non-accrual investments, which represent 0.6% of the total investment portfolio at fair value and 3.2% at cost Weighted-average effective yield of 12.5%(4) ● ● ● Geography End markets Vintage Other Portfolio also includes the External Investment Manager and short-term portfolio investments, each as described in MAIN's filings with the Securities Exchange Commission (the SEC) (1) (2) As of March 31, 2023; based on cost (3) Based upon total investment income for the trailing twelve month period ended March 31, 2023 (4) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 20#21Total Portfolio by Industry (as a Percentage of Cost)(1) ■ Internet Software & Services, 8% Commercial Services & Supplies, 7% ■ Distributors, 5% ■ Professional Services, 5% ■Leisure Equipment & Products, 5% ■Specialty Retail, 3% ■ Tobacco, 3% ■ Media, 2% ■ Computers & Peripherals, 2% ■ Software, 2% ■ Communications Equipment, 2% ■Auto Components, 2% ■ Electronic Equipment, Instruments & Components, 2% ■Health Care Equipment & Supplies, 1% ■Chemicals, 1% ■Hotels, Restaurants & Leisure, 1% Machinery, 7% Construction & Engineering, 6% ■Health Care Providers & Services, 5% ■Diversified Consumer Services, 5% ■IT Services, 4% ■ Energy Equipment & Services, 3% ■Containers & Packaging, 3% ■Aerospace & Defense, 2% Building Products, 2% ■Textiles, Apparel & Luxury Goods, 2% ■ Diversified Telecommunication Services, 2% ■Food Products, 2% ■Diversified Financial Services, 1% ■Intemet & Catalog Retail, 1% ■Food & Staples Retailing, 1% ■Other, 3% MAIN ST NYSE: MAIN CAPITAL CORPORATION (1) Excluding MAIN's Other Portfolio investments, the External Investment Manager and short-term portfolio investments, each as described in MAIN's filings with the SEC, which in aggregate represent approximately 4% of the total portfolio Main Street Capital Corporation mainstcapital.com Page 21#22Diversified Total Portfolio (as a Percentage of Cost)(1) Invested Capital by Transaction Type LBO/MBO Acquisition 43% 11% 4% Growth Capital 42% Recapitalization/ Refinancing Invested Capital by Geography (²) 29% 20% NYSE: MAIN 17% MAIN ST CAPITAL CORPORATION 14% 20% (1) Excluding MAIN's Other Portfolio investments, the External Investment Manager and short-term portfolio investments, each as described in MAIN's filings with the SEC, which in aggregate represent approximately 4% of the total portfolio (2) Based upon portfolio company headquarters and excluding any MAIN investments headquartered outside the U.S., which in aggregate represent approximately 2% of the total portfolio Main Street Capital Corporation mainstcapital.com Page 22#23LMM Investment Portfolio LMM investment portfolio consists of a diversified mix of secured debt and lower cost basis equity investments 79 portfolio companies / $2.1 billion in fair value ● 51% of total investment portfolio at fair value ● Debt yielding 12.6% (¹) (73% of LMM portfolio at cost) 99% of debt investments have first lien position 63% of debt investments earn fixed-rate interest ● ● ● ● Equity ownership in all LMM portfolio companies representing 41% average ownership position (27% of LMM portfolio at cost) Opportunity for dividend income, fair value appreciation and ● ● MAIN ST ● CAPITAL CORPORATION Approximately 830 basis point net cash interest margin vs "matched" fixed interest rate on SBIC debentures and Notes Payable periodic capital gains 64% of LMM companies (2) with direct equity investment are currently paying dividends Fair value appreciation of equity investments supports Net Asset Value per share growth Lower entry multiple valuations, lower cost basis $384.7 million, or $4.82 per share, of cumulative pre-tax net unrealized appreciation at March 31, 2023 (1) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status NYSE: MAIN (2) Includes the LMM companies that (a) MAIN has a direct equity investment and (b) are flow-through entities for tax purposes; based upon dividend income for the trailing twelve month period ended March 31, 2023 Main Street Capital Corporation mainstcapital.com Page 23#24LMM Investment Portfolio LMM investment portfolio is a pool of high quality, seasoned assets with attractive risk-adjusted return characteristics ● Median LMM portfolio credit statistics (¹): Senior leverage of 2.9x EBITDA through MAIN debt position 2.6x EBITDA to senior interest coverage Total leverage of 3.1x EBITDA including debt junior in priority to MAIN ● ● MAIN ST CAPITAL CORPORATION Average investment size of $26.7 million at fair value or $21.9 million on a cost basis (less than 1% of total investment portfolio) ● Free cash flow de-leveraging improves credit metrics and increases equity appreciation Opportunistic, selective posture toward new investment activity over the economic cycle ● High quality, seasoned LMM portfolio Total LMM portfolio investments at fair value equals 122% of cost Equity component of LMM portfolio at fair value equals 191% of cost Significant portion of LMM portfolio has de-leveraged and a majority of the LMM portfolio investments have experienced equity appreciation (1) These credit statistics exclude portfolio companies on non-accrual and four companies for which EBITDA is not a meaningful metric Main Street Capital Corporation NYSE: MAIN - 50 LMM portfolio companies with unrealized appreciation on equity investments Net unrealized appreciation on LMM Equity investments of $427.2 million mainstcapital.com Page 24#25LMM Portfolio by Industry (as a Percentage of Cost) ■Machinery, 11% Construction & Engineering, 7% ■Containers & Packaging, 5% Diversified Consumer Services, 4% ■ Distributors, 4% ■Auto Components, 4% Electronic Equipment, Instruments & Components, 3% Textiles, Apparel & Luxury Goods, 3% ■Specialty Retail, 3% ■Health Care Providers & Services, 2% ■ Media, 2% Hotels, Restaurants & Leisure, 2% ■Household Products, 1% ■ Other, 3% Main Street Capital Corporation ■ Professional Services, 7% ■ Tobacco, 7% ■ Computers & Peripherals, 5% ■IT Services, 4% ■ Leisure Equipment & Products, 4% ■ Software, 4% ■Household Durables, 1% ■ Building Products, 1% MAIN ST ■ Energy Equipment & Services, 3% ■Internet Software & Services, 3% ■Food Products, 3% ■ Internet & Catalog Retail, 2% ■Health Care Equipment & Supplies, 2% NYSE: MAIN CAPITAL CORPORATION mainstcapital.com Page 25#26Diversified LMM Portfolio (as a Percentage of Cost) Invested Capital by Transaction Type LBO/MBO 27% Acquisition 6% 3% Growth Capital (1) Based upon portfolio company headquarters Main Street Capital Corporation Recapitalization/ Refinancing 64% Invested Capital by Geography (¹) NYSE: MAIN 28% 22% 26% MAIN ST CAPITAL CORPORATION 14% 10% mainstcapital.com Page 26#27LMM Portfolio Attributes Reflect Investment Strategy High yielding secured debt investments coupled with significant equity participation = Attractive risk-adjusted returns Weighted-Average Effective Yield on Debt Investments = 12.6% (1) Average Fully Diluted Equity Ownership = 41% Security Position on Debt Capital as a Percentage of Cost 1st Lien 99% 2nd Lien/ Other 1% 50.0% and greater MAIN ST Fully Diluted Equity Ownership % 33% CAPITAL CORPORATION 38% 29% 25.0% - 49.9% 1.0% - 24.9% (1) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 27#28Term and Total Interest Coupon of Existing LMM Debt Investments Original Term < 5 years 6% 90% 4% > 5 years 5 years Total Interest Coupon(¹) N/A - Floating Interest Rate (Wtd. Avg. of 13.6%) (²) <10% Current Interest 38% 4% 12% 10% Current Interest 7% 2% MAIN ST CAPITAL CORPORATION 14% Current Interest 11% 26% 11% Current Interest 13% Current Interest 12% Current Interest Debt Investments generally have a 5-Year Original Term and ~3.2 Year Weighted-Average Remaining Duration; Weighted-Average Effective Yield of 12.6% (³) on Debt Portfolio (1) Interest coupon excludes amortization of deferred upfront fees, original issue discount, exit fees and any debt investments on non-accrual status (2) Floating interest rates generally include contractual minimum "floor" rates; Interest rate of 13.6% is based on weighted-average principal balance of floating rate debt investments as of March 31, 2023 (3) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 28#29Private Loan Investment Portfolio Private Loan investment portfolio provides a diversified mix of investments and sources of income to complement the LMM investment portfolio 86 investments / $1.5 billion in fair value 36% of total investment portfolio at fair value Average investment size of $17.8 million(¹) (less than 1% of total portfolio) ● Investments in secured debt instruments 97% of Private Loan portfolio is secured debt 99% of Private Loan debt portfolio is first lien term debt ● MAIN ST ● CAPITAL CORPORATION Debt yielding 12.4% (²) 98% of Private Loan debt investments bear interest at floating (1) rates(3), providing matching with MAIN's floating rate Credit Facilities (4) ● Approximately 525 basis point effective interest margin vs "matched" floating rate on MAIN's Credit Facilities (4) NYSE: MAIN (1) As of March 31, 2023; based on cost (2) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status (3) 95% of floating interest rates on Private Loan debt investments are subject to contractual minimum "floor" rates (4) Includes MAIN's Credit Facilities as defined on page 11; see additional details on page 42 Main Street Capital Corporation mainstcapital.com Page 29#30Middle Market Investment Portfolio Middle Market investment portfolio provides a diversified mix of investments and diverse sources of income to complement the LMM investment portfolio and represents a potential source of liquidity for MAIN's future investment activities 30 investments / $306.2 million in fair value 7% of total investment portfolio at fair value Average investment size of $13.0 million(¹) (less than 1% of total portfolio) ● Investments in secured and/or rated debt investments 94% of Middle Market portfolio is secured debt 99% of Middle Market debt portfolio is first lien term debt ● MAIN ST ● CAPITAL CORPORATION Debt yielding 11.8% (2) 95% of Middle Market debt investments bear interest at floating (1) rates(3), providing matching with MAIN's floating rate Credit Facilities (4) ● Over 450 basis point effective interest margin vs "matched" floating rate on MAIN's Credit Facilities (4) NYSE: MAIN (1) As of March 31, 2023; based on cost (2) Weighted-average effective yield is calculated using the applicable interest rate as of March 31, 2023 and includes amortization of deferred debt origination fees and accretion of original issue discount, but excludes fees payable upon repayment of the debt instruments and any debt investments on non-accrual status (3) 80% of floating interest rates on Middle Market debt investments are subject to contractual minimum "floor" rates (4) Includes MAIN's Credit Facilities as defined on page 11; see additional details on page 42 Main Street Capital Corporation mainstcapital.com Page 30#31Private Loan & Middle Market Portfolios by Industry (as a Percentage of Cost) ■ Internet Software & Services, 13% Health Care Providers & Services, 7% ■ Leisure Equipment & Products, 5% ■ Diversified Consumer Services, 5% ■Specialty Retail, 4% ■ Energy Equipment & Services, 3% ■IT Services, 3% ■ Building Products, 3% ■ Media, 2% ■ Food & Staples Retailing, 2% ■ Pharmaceuticals, 2% ■ Textiles, Apparel & Luxury Goods, 1% Main Street Capital Corporation ■ Commercial Services & Supplies, 12% ■ Distributors, 6% ■ Construction & Engineering, 5% ■ Aerospace & Defense, 5% ■Machinery, 4% MAIN ST NYSE: MAIN CAPITAL CORPORATION ■Communications Equipment, 3% ■ Diversified Telecommunication Services, 3% ■Professional Services, 3% ■Chemicals, 2% ■ Diversified Financial Services, 2% ■ Electrical Equipment, 1% ■ Other, 4% mainstcapital.com Page 31#32Diversified Private Loan & Middle Market Investments (as a Percentage of Cost) Invested Capital by Transaction Type LBO/MBO 57% Acquisition 15% 5% Recapitalization/ Refinancing 23% Growth Capital Invested Capital by Geography (¹) 30% NYSE: MAIN 17% 9% MAIN ST CAPITAL CORPORATION 15% 29% (1) Based upon portfolio company headquarters and excluding any MAIN investments headquartered outside the U.S., which in aggregate represent approximately 4% of the combined Private Loan and Middle Market portfolios Main Street Capital Corporation mainstcapital.com Page 32#33Main Street Capital Corporation Financial Overview Main Street Capital Corporation 1st Quarter 2023 NYSE: MAIN MAIN ST - CAPITAL CORPORATION mainstcapital.com Page 33#34MAIN Financial Performance Total Investment Income ($ in millions) Year over Year Change 4% (9)% 30% $400.0 $360.0 $320.0 $280.0 $240.0 $200.0 $160.0 $120.0 $80.0 $40.0 $0.0 EN $233.4 $243.4 2018 2019 $222.6 $289.0 30% $376.9 2020 2021 2022 51% (2) $120.3 YTD 2023 (3) $275.0 $250.0 $225.0 $200.0 $175.0 $150.0 $165.6 $168.3 $125.0 $100.0 $75.0 $50.0 $25.0 $0.0 Distributable Net Investment Income(¹) ($ in millions) Year over Year Change 2% (11)% 30% 2018 2019 NYSE: MAIN $149.6 See reconciliation of DNII to Net Investment Income on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (2) Reflects year-to-date March 31, 2023 performance compared to March 31, 2022 (3) Three months ended March 31, 2023 Main Street Capital Corporation 2020 MAIN ST CAPITAL CORPORATION $194.7 2021 32% $257.5 2022 56% (2) $85.4 YTD 2023 (3) mainstcapital.com Page 34#35Long-Term Portfolio and DNII(¹) Per Share Growth MAIN has consistently grown portfolio investments and DNII per share Portfolio Investments(2) ($ in millions, except per share data) $4,800 $4,600 $4,400 $4,200 $4,000 $3,800 $3,600 $3,400 $3,200 $3,000 $2,800 $2,600 $2,400 $2,200 $2,000 $1,800 $1,600 $1,400 $1,200 $1,000 $800 $600 $400 $200 $0 $0.76 $1.19 $1.25 $1.02 $408 $2.09 $1.77 $658 $924 $2.17 $2.29 $1,286 $2.31 $1,563 $2.39 $1,800 NYSE: MAIN $2.57 Portfolio Investments $2.75 $2.67 $2,171 $1,997! $2,454 $2.28 $2,685 -DNII per Share MAIN ST CAPITAL CORPORATION $2.82 $3,562 (1) $106 $127 $159 2007 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 March $3.46 $3.62 $4,1024,161 (1) See reconciliation of DNII per share to Net Investment Income per share on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (2) Based on fair value at the end of the period (3) DNII per share for the trailing twelve month period ended March 31, 2023 Main Street Capital Corporation 31, 2023 (3) $3.80 $3.60 $3.40 $3.20 $3.00 $2.80 $2.60 $2.40 $2.20 $2.00 $1.80 $1.60 $1.40 $1.20 $1.00 $0.80 $0.60 $0.40 $0.20 $0.00 mainstcapital.com Page 35 DNII per share(1)#36Efficient and Leverageable Operating Structure MAIN's internally managed operating structure provides significant operating leverage and greater returns for our shareholders "Internally managed" structure means no external management fees or expenses are paid ● MAIN ST Alignment of interest between management and investors Greater incentives to maximize increases to shareholder value and rationalize debt and equity capital raises 100% of MAIN's management efforts and activities are for the benefit of MAIN investors CAPITAL CORPORATION ● MAIN targets total operating expenses (¹) as a percentage of average assets (Operating Expense to Assets Ratio) at or less than 2% Long-term actual results have significantly outperformed target An industry leading position in cost efficiency, with an Operating Expense to Assets Ratio of 1.4% (²) Significant portion of total operating expenses (¹) are non-cash Non-cash compensation expenses (³) were 24.9% (2) of total operating expenses (1) (1) Total expenses excluding interest expense (2) Based upon the trailing twelve month period ended March 31, 2023 (3) See calculation of non-cash compensation expenses on page 38 and non-GAAP information disclosures on page 48 of this presentation Main Street Capital Corporation NYSE: MAIN Operating Expense to Assets Ratio of 1.1% (2) excluding non-cash compensation expenses(3) mainstcapital.com Page 36#37MAIN Maintains a Significant Operating Cost Advantage Operating Expenses (¹) as a Percentage of Total Assets 3.0% 2.5% 2.0% 1.5% 1.0% 0.5% 0.0% MAIN (2) MAIN Excl. Non-cash Comp Exp (3)(4) Other BDCs (4)(5)(6) Other BDCS Excl. Non-cash Comp Exp (4)(5)(7) MAIN ST CAPITAL CORPORATION 1 Commercial Banks (8) (1) Total expenses excluding interest expense (2) Based upon the trailing twelve month period ended March 31, 2023 (3) Based upon the trailing twelve month period ended March 31, 2023, excluding non-cash compensation expenses (4) See calculation of non-cash compensation expenses on page 38 and non-GAAP information disclosures on page 48 of this presentation (5) Other BDCs includes dividend paying BDCs that have been publicly-traded for at least two years and have total assets greater than $500 million based on individual SEC Filings as of December 31, 2022; specifically includes: ARCC, BBDC, BCSF, BKCC, CCAP, CGBD, CSWC, FDUS, FSK, GAIN, GBDC, GLAD, GSBD, HRZN, HTGC, MFIC, MRCC, NMFC, OCSL, OFS, ORCC, PFLT, PNNT, PSÉC, PTMN, SAR, SCM, SLRC, TCPC, TPVG, TSLX and WHF NYSE: MAIN (6) Calculation represents the average for the companies included in the group and is based upon the trailing twelve month period ended December 31, 2022 as derived from each company's SEC filings, including non-cash compensation expenses (7) Calculation represents the average for the companies included in the group and is based upon the trailing twelve month period ended December 31, 2022 as derived from each company's SEC filings, excluding non-cash compensation expenses (8) Source: SNL Financial; calculation represents the average for the trailing twelve month period ended December 31, 2022 and includes commercial banks with a market capitalization between $500 million and $3 billion Main Street Capital Corporation mainstcapital.com Page 37#38MAIN Income Statement Summary ($ in 000's), except per share amounts Total Investment Income Expenses: Interest Expense G&A Expense (²) Distributable Net Investment Income (DNII)(2)(3) DNII Margin % Non-Cash Compensation Expenses (³) Share-based Compensation Expense Deferred Compensation (Expense) Benefit Total Non-Cash Compensation Expenses (³) Net Investment Income Net Realized Gain (Loss) Net Unrealized Appreciation (Depreciation) Income Tax Provision Net Increase in Net Assets Net Investment Income Per Share DNII Per Share (³) $ $ $ $ Q1 22 Q2 22 79,395 $ 85,200 $ (16,687) (8,054) 54,654 68.8% (2,818) 376 (2,442) 52,212 3,336 14,752 (5,097) 65,203 $ 0.73 $ 0.76 $ (17,295) (10,808) 57,097 67.0% (3,596) 1,225 (2,371) 54,726 (5,064) (24,593) (10,320) 14,749 $ 0.75 $ 0.78 $ Q3 22 (3) See Non-GAAP Information disclosures on page 48 of this presentation (4) Change in DNII Margin is based upon the basis point difference (increase/(decrease)) NM Not Measurable / Not Meaningful Main Street Capital Corporation 98,387 (21,234) (11,386) 65,767 66.8% $ (3,617) 298 (3,319) 62,448 5,031 (10,081) (2,060) 55,338 $ 0.83 $ 0.88 NYSE: MAIN Q4 22 113,876 (23,060) (10,812) 80,004 70.3% $ Positive percentage represents an increase and negative percentage represents a decrease to the Net Increase (Decrease) in Net Assets (2) Excludes non-cash compensation expenses (3,598) (466) (4,064) 75,940 (8,515) 44,738 (5,848) 106,315 $ 0.98 $ 1.03 $ Q1 23 120,254 (24,997) (9,814) 85,443 MAIN ST (4,100) (376) (4,476) 80,967 (28,379) 35,118 (8,114) 79,592 1.02 1.07 CAPITAL CORPORATION 71.1% Q1 23 vs. Q1 22 Change (¹) 51% (50)% (22)% 56% 225 bps (45)% NM (83)% 55% NM NM NM 22% 40% 41% (4) mainstcapital.com Page 38#39MAIN Per Share Change in Net Asset Value (NAV) ($ per share) Beginning NAV Distributable Net Investment Income (1) Non-Cash Compensation Expenses(¹) Net Realized Gain (Loss) Net Unrealized Appreciation (Depreciation) Income Tax Provision Net Increase in Net Assets Regular Monthly Dividends to Shareholders Supplemental Dividends to Shareholders Accretive Impact of Stock Offerings (2) Other (3) Ending NAV Weighted Average Shares Q1 22 25.29 0.76 (0.03) 0.05 0.20 (0.07) 0.91 (0.645) (0.08) 0.38 0.03 25.89 $ 71,708,326 Q2 22 25.89 $ 0.78 (0.03) (0.07) (0.34) (0.14) 0.20 (0.645) (0.075) 0.15 (0.15) 25.37 $ 73,304,619 Q3 22 25.37 0.88 (0.05) 0.07 NYSE: MAIN (0.13) (0.03) 0.74 (0.645) (0.1) 0.53 0.05 25.94 $ 75,036,522 Q4 22 MAINST CAPITAL CORPORATION 25.94 1.03 (0.05) (0.12) 0.60 (0.07) 1.39 (0.66) (0.10) 0.20 0.09 26.86 77,802,377 $ Q1 23 26.86 1.07 (0.05) (0.36) 0.44 (0.10) 1.00 (0.675) (0.175) 0.18 0.04 27.23 79,552,200 Certain fluctuations in per share amounts are due to rounding differences between quarters. (1) See reconciliation of non-cash compensation expenses and DNII per share to Net Investment Income per share on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (2) Includes accretive impact of shares issued through the Dividend Reinvestment Plan (DRIP), the At-the-Market (ATM) equity issuance program and the equity offering in August 2022 (3) Includes differences in weighted-average shares utilized for calculating changes in NAV during the period and actual shares outstanding utilized in computing ending NAV and other minor changes Main Street Capital Corporation mainstcapital.com Page 39#40MAIN Balance Sheet Summary ($ in 000's, except per share amounts) LMM Portfolio Investments Private Loan Investments Middle Market Portfolio Investments Other Portfolio Investments External Investment Manager Short-term Investments Cash and Cash Equivalents Other Assets Total Assets Credit Facilities SBIC Debentures Notes Payable(¹) Other Liabilities Net Asset Value (NAV) Total Liabilities and Net Assets Total Portfolio Fair Value as % of Cost Common Stock Price Data: High Close Low Close Quarter End Close $ $ $ $ $ Q1 22 1,795,456 1,260,664 397,338 102,392 132,920 1,968 17,952 72,293 3,780,983 338,000 343,027 1,133,472 92,830 1,873,654 3,780,983 109 % 44.88 39.94 42.64 $ $ $ $ Q2 22 1,816,255 $ 1,309,020 363,468 108,846 118,320 1,861 43,383 64,592 3,825,745 $ 380,000 $ 343,323 1,133,618 103,641 1,865,163 3,825,745 $ 109 % 43.65 34.59 38.53 $ Q3 22 NYSE: MAIN 1,910,915 1,476,934 354,286 117,010 112,490 1,855 61,158 100,318 4,134,966 561,000 343,618 1,133,766 117,162 1,979,420 108 % Q4 22 2,060,459 1,471,466 329,119 116,299 122,930 1,904 49,121 90,587 $ 4,241,885 607,000 343,914 1,048,188 134,197 2,108,586 4,134,966 $ 45.28 33.23 33.64 $ $ 4,241,885 109 % 39.50 32.57 36.95 $ $ MAINST CAPITAL CORPORATION Q1 23 2,112,619 1,491,395 306,243 116,067 132,650 1,943 39,752 92,586 4,293,255 564,000 328,206 1,097,435 130,692 2,172,922 4,293,255 110% 42.49 36.87 39.46 (1) Includes $500.0 million of July 2026 Notes, $450.0 million of May 2024 Notes, $185.0 million of December 2022 Notes (repaid Q4 2022) and $150.0 million of December 2025 Notes (100.0 million issued in Q4 2022 and $50.0 million issued in Q1 2023) Main Street Capital Corporation mainstcapital.com Page 40#41MAIN Liquidity and Capitalization ($ in 000's) Cash and Cash Equivalents Availability Under Credit Facilities (1) Total Liquidity Debt at Par Value: Credit Facilities (1) SBIC Debentures Notes Payable (2) Total Debt Net Asset Value (NAV) Total Capitalization Debt to NAV Ratio (3) Non-SBIC Debt to NAV Ratio (4) (5) Net Debt to NAV Ratio (5) (6) Interest Coverage Ratio (7) $ $ $ Q1 22 17,952 517,000 534,952 $ 338,000 $ 350,000 1,135,000 1,823,000 1,873,654 3,696,654 0.97 to 1.0 0.79 to 1.0 0.96 to 1.0 4.35 to 1.0 Q2 22 43,383 475,000 518,383 $ 380,000 $ 350,000 1,135,000 1,865,000 1,865,163 3,730,163 1.00 to 1.0 0.81 to 1.0 0.98 to 1.0 4.38 to 1.0 $ Q3 22 61,158 359,000 420,158 $ NYSE: MAIN $ 561,000 $ 350,000 1,135,000 2,046,000 1,979,420 4,025,420 1.03 to 1.0 0.86 to 1.0 1.00 to 1.0 4.26 to 1.0 Q4 22 (5) See reconciliation of DNII to Net Investment Income on page 38 and Non-GAAP Information disclosures on page 48 of this presentation (6) Net debt in this ratio includes par value of total debt less cash and cash equivalents (7) DNII(5) + interest expense / interest expense on a trailing twelve month basis Main Street Capital Corporation MAIN ST CAPITAL CORPORATION 49,121 568,000 617,121 607,000 350,000 1,050,000 2,007,000 2,108,586 4,115,586 0.95 to 1.0 0.79 to 1.0 0.93 to 1.0 4.29 to 1.0 $ $ Q1 23 39,752 671,000 710,752 564,000 334,000 1,100,000 1,998,000 2,172,922 4,170,922 0.92 to 1.0 0.77 to 1.0 0.90 to 1.0 (1) As of March 31, 2023, MAIN's Corporate Facility had $980.0 million in total commitments with an accordion feature with the right to request an increase up to $1.4 billion and MAIN's SPV Facility had $255.0 million in total commitments with an accordion feature with the right to request an increase up to $450.0 million; borrowings under these Credit Facilities are available to provide additional liquidity for investment and operational activities; see additional detail on page 42 (2) Includes $500.0 million of July 2026 Notes, $450.0 million of May 2024 Notes, $185.0 million of December 2022 Notes (repaid Q4 2022) and $150.0 million of December 2025 Notes (100.0 million issued in Q4 2022 and $50.0 million issued in Q1 2023) 4.33 to 1.0 (3) SBIC Debentures are not included as "senior debt" for purposes of the BDC asset coverage requirements pursuant to exemptive relief received by MAIN; Debt to NAV Ratio is calculated based upon the par value of debt (4) Non-SBIC Debt to NAV Ratio is calculated based upon the par value of debt of both the Credit Facilities and notes payable mainstcapital.com Page 41#42MAIN maintains a conservative capital structure, with limited overall leverage and an intentional mix of secured, floating rate revolving debt and unsecured, fixed rate long-term debt E Stable, Long-Term Leverage - Significant Unused Capacity Facility $980.0 million Corporate Facility $255.0 million SPV Facility(2)(3) Notes Payable Capital structure is designed to correlate to and complement the expected duration and fixed/floating rate Notes Payable nature of investment portfolio assets Notes Payable SBIC Debentures Interest Rate SOFR+1.875% floating (6.6% (4)) SOFR+2.50% floating (7.3% (4)) 3.00% fixed 5.20% fixed 7.74% (5) fixed (weighted average) 2.87% fixed (weighted average) Maturity August 2027(1) MAIN ST November 2027(²) CAPITAL CORPORATION Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures July 14, 2026 Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures May 1, 2024 Redeemable at MAIN's option at any time, subject to certain make whole provisions; Matures December 23, 2025 Various dates between 2023 - 2031 (weighted average duration = 5.1 years) Principal Drawn $394.0 million $170.0 million $500.0 million $450.0 million $150.0 million $334.0 million (1) As of March 31, 2023, MAIN maintained a corporate revolving line of credit (the Corporate Facility), which had $980.0 million in total commitments with an accordion feature with the right to request an increase up to $1.4 billion; MAIN's Corporate Facility is fully revolving until August 2026, with a maturity date in August 2027 (2) As of March 31, 2023, MAIN tained a secured special purpose veh financing facility (the SPV Facility), which had $255.0 million in total co tments with an accordion feature with the right to request an increase up to $450.0 million; MAIN's SPV Facility is fully revolving until November 2025, with a maturity date in November 2027 (3) Borrowings under the Corporate Facility and the SPV Facility (together, the Credit Facilities) are available to provide additional liquidity for investment and operational activities (4) Credit Facilities' rates reflect the rate based on SOFR as of March 31, 2023 and effective as of the contractual reset date as of April 1, 2023 (5) Based upon $100.0 million and $50.0 million in aggregate principal amount bearing interest at 7.84% and 7.53%, respectively Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 42#43Long-term Maturity of Debt Obligations MAIN's conservative capital structure provides long-term access to attractively- priced and structured debt facilities ● Allows for investments in assets with long-term holding periods / illiquid positions and greater yields and overall returns Provides downside protection and liquidity through economic cycles Allows MAIN to be opportunistic during periods of economic uncertainty (in millions) $900 $850 $800 $750 $700 $650 $600 $550 $500 $450 $400 $350 $300 $250 $200 $150 $100 $50 $0 2023 $450.0 $63.8 2024 $150.0 2025 SBIC debentures December 2025 Notes' (3) $500.0 2026 $564.0 $75.0 2027 Credit Facilities (1) July 2026 Notes (4) $75.0 2028 2029 MAIN ST CAPITAL CORPORATION May 2024 Notes(2) $35.0 2030 (1) See page 42 for further detail related to MAIN's Credit Facilities (2) Issued in April 2019; with follow-on issuances in December 2019 and July 2020; redeemable at MAIN's option at any time, subject to certain make-whole provisions (3) Issued in December 2022; with a follow-on issuance in February 2023; redeemable at MAIN's option at any time, subject to certain make-whole provisions (4) Issued in January 2021; with a follow-on issuance in October 2021; redeemable at MAIN's option at any time, subject to certain make-whole provisions Main Street Capital Corporation NYSE: MAIN $85.2 2031 mainstcapital.com Page 43#44Interest Rate Impact and Sensitivity MAIN's financial results are subject to impact from changes in interest rates; MAIN's capital structure includes a majority of fixed rate debt obligations, while MAIN's investment portfolio includes a majority of floating rate debt investments with minimum interest rate floors - 72% of MAIN's outstanding debt obligations have fixed interest rates (5), limiting the increase in interest expense - 73% of MAIN's debt investments bear interest at floating rates(5), the majority of which contain contractual minimum index rates, or "interest rate floors" (weighted-average floor of approximately 110 basis points)(6) - Provides MAIN the opportunity to achieve increases in net investment income if market interest rates increase, but also results in reductions to net investment income if market interest rates decrease Main Street Capital Corporation Basis Point Increase (Decrease) in Interest Rate The following table illustrates the approximate annual changes in the components of MAIN's net investment income due to hypothetical increases (decreases) in interest rates (1)(2) (dollars in thousands, except per share data): (100) (75) (50) (25) 25 50 75 100 $ Increase (Decrease) in Interest Income (23,523) $ (17,873) (12,223) (6,574) 4,736 10,375 16,025 21,675 (Increase) Decrease in Interest Expense (3) NYSE: MAIN MAIN ST 6,204 $ 4,794 3,384 1,974 (846) (2,256) (3,666) (5,076) CAPITAL CORPORATION Increase (Decrease) in Net Investment Income Increase (Decrease) in Net Investment Income Share Der (17,319) $ (13,079) (8,839) (4,600) 3,890 8,119 12,359 16,599 (0.22) (0.16) (0.11) (0.06) 0.05 0.10 0.15 0.21 (1) Assumes no changes in the portfolio investments, outstanding borrowings on the Credit Facilities (as defined on page 42)or other debt obligations existing as of March 31, 2023 (2) Assumes that all LIBOR, SOFR and Prime rates would change effective immediately on the first day of the period; however, the actual contractual index rate reset dates will vary in future periods generally on either a monthly or quarterly basis across both our debt investments and our Credit Facilities resulting in a delay in the realization of the increases or decreases in interest income (3) The hypothetical (increase) decrease in interest expense would be impacted by the changes in the amount of debt outstanding under our Credit Facilities, with interest expense (increasing) decreasing as the debt outstanding under our Credit Facilities increases (decreases) (4) Per share amount is calculated using shares outstanding as of March 31, 2023 (5) As of March 31, 2023, based on par (6) Weighted-average interest rate floor calculated based on debt principal balances as of March 31, 2023 Although we believe that this analysis is indicative of the impact of interest rate changes to our net investment income as of March 31, 2023, the analysis does not take into consideration future changes in the credit market, credit quality or other business or economic developments that could affect our net investment income. Accordingly, we can offer no assurances that actual results would not differ materially from the analysis above. mainstcapital.com Page 44#45Significant Management Ownership / Investment # of Shares (2) 3,293,812 Significant equity ownership by MAIN's management team, coupled with internally managed structure, provides alignment of interest between MAIN's management and our shareholders Management (1) MAINST NYSE: MAIN CAPITAL CORPORATION Market Value (3) $129,973,822 (1) Includes members of MAIN's executive and senior management team and the members of MAIN's Board of Directors (2) Includes 1,238,532 shares, or approximately $34.0 million, purchased by management as part of, or subsequent to, the MAIN IPO, including 19,375 shares, or approximately $0.8 million, purchased, directly or through MAIN's dividend reinvestment plan, in the quarter ended March 31, 2023 (3) Based upon closing market price of $39.46/share on March 31, 2023 Main Street Capital Corporation mainstcapital.com Page 45#46MAIN Total Return(2) Performance Since IPO $1200 $1000 $800 $600 $400 $200 $0 2008 2009 TOTAL RETURN PERFORMANCE SINCE MAIN IPO 2010 2011 2012 MAIN (855.96%) (1) S&P BDC Index (-54.52%) (4) 2013 2014 Notes: (1) Assumes dividends reinvested on date paid (2) Indexed as of October 5, 2007 and last trading date is March 31, 2023 (3) 2015 S&P 500 (261.00%) 2016 2017 2018 Russell 2000 (163.71%) 2019 NYSE: MAIN 2020 2021 2022 MAIN ST CAPITAL CORPORATION 2023 KBW Regional Bank Index (-0.29%)(3) $1200 $1000 $800 $600 $400 $200 $0 The KBW Nasdaq Regional Banking Index is a modified market capitalization weighted index designed to track the performance of U.S. regional banks or thrifts that are publicly traded in the U.S. (4) The S&P BDC Index measures the performance of Business Development Companies that trade on major U.S. exchanges; Constituents are float-adjusted market capitalization (FMC) weighted, subject to a single constituent weight cap of 10% Main Street Capital Corporation mainstcapital.com Page 46#47Executive Summary Unique focus on under-served Lower Middle Market Inefficient asset class with less competition Unique market opportunity with attractive risk-adjusted returns Generally first lien, senior secured debt investments plus meaningful equity participation ● ● ● ● Invest in complementary interest-bearing Private Loan and Middle Market debt investments • Lower risk / more liquid asset class Opportunity for consistent investment activity Generally first lien, senior secured debt investments Growing Asset Management Business drives additional investment income Efficient internally managed operating structure drives greater shareholder returns Alignment of interests between management and our shareholders Maintains an industry leading operating cost structure Favorable operating cost comparison to other yield oriented investment options ● ● ● ● Attractive, recurring monthly dividend yield and historical net asset value per share growth Periodic increases in monthly dividends Increase in net asset value per share creates opportunity for stock price appreciation Additional dividend income through periodic supplemental dividends Strong liquidity and stable capitalization for sustainable growth Highly invested management team with successful track record Niche investment strategy with lower correlation to broader debt / equity markets Main Street Capital Corporation ● MAIN ST ● CAPITAL CORPORATION NYSE: MAIN mainstcapital.com Page 47#48Non-GAAP Information Distributable net investment income is net investment income as determined in accordance with U.S. Generally Accepted Accounting Principles, or U.S. GAAP, excluding the impacts of non-cash compensation expenses (as defined below). MAIN believes presenting distributable net investment income and the related per share amounts is useful and appropriate supplemental disclosure for analyzing our financial performance since non-cash compensation expenses do not result in a net cash impact to Main Street upon settlement. However, distributable net investment income is a non-U.S. GAAP measure and should not be considered as a replacement for net investment income or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing MAIN's financial performance. Non-cash compensation expenses consist of (i) share-based compensation and (ii) deferred compensation expense or benefit, both of which are non-cash in nature. Share-based compensation does not require settlement in cash. Deferred compensation expense or benefit does not result in a net cash impact to Main Street upon settlement. The appreciation (depreciation) in the fair value of deferred compensation plan assets is reflected in Main Street's Consolidated Statements of Operations as unrealized appreciation (depreciation) and an increase (decrease) in compensation expenses, respectively. Main Street believes presenting non-cash compensation expenses is useful and appropriate supplemental disclosure for analyzing its financial performance since non-cash compensation expenses do not result in a net cash impact to Main Street upon settlement. However, non-cash compensation expenses are non-U.S. GAAP measures and should not be considered as a replacement for compensation expenses, total expenses or other earnings measures presented in accordance with U.S. GAAP and should be reviewed only in connection with such U.S. GAAP measures in analyzing Main Street's financial performance. Main Street Capital Corporation MAIN ST NYSE: MAIN CAPITAL CORPORATION Net Debt to NAV Ratio is calculated as the Debt to NAV Ratio as determined in accordance with U.S. GAAP, except that total debt is reduced by cash and cash equivalents. The Non-SBIC Debt to NAV Ratio is calculated in the same manner as the Debt to NAV Ratio, except that outstanding SBIC debentures are excluded from the debt pursuant to an exemptive order MAIN received from the Securities and Exchange Commission. MAIN believes presenting the Net Debt to NAV Ratio is useful and appropriate supplemental disclosure for analyzing its financial position and leverage. MAIN believes presenting the Non-SBIC Debt to NAV Ratio is useful and appropriate supplemental disclosure because Main Street, a business development company, is permitted to exclude such borrowings from its regulatory asset coverage ratio calculation pursuant to an exemptive order received from the Securities and Exchange Commission. However, the Net Debt to NAV Ratio and the Non-SBIC Debt to NAV Ratio are non-U.S. GAAP measures and should not be considered as replacements for the Debt to NAV Ratio and other financial measures presented in accordance with U.S. GAAP. Instead, the Net Debt to NAV Ratio and the Non-SBIC Debt to NAV Ratio should be reviewed only in connection with such U.S. GAAP measures in analyzing MAIN's financial position. mainstcapital.com Page 48#49MAIN Corporate Data Please visit our website at www.mainstcapital.com for additional information Board of Directors Executive Officers Research Coverage Vincent D. Foster Dwayne L. Hyzak Chairman of the Board Chief Executive Officer Vilas Abraham & Marissa Lobo UBS (212) 713-3241 (212) 713-3922 Main Street Capital Corporation Board of Directors Quanta Services, Inc. J. Kevin Griffin Chief Strategy Officer MaineHealth Dwayne L. Hyzak CEO Main Street Capital Corporation John E. Jackson President & CEO CSI Compressco LP Brian E. Lane CEO & President Comfort Systems USA Dunia A. Shive Board of Directors DallasNews Corporation, Kimberly-Clark Corporation and Trinity Industries, Inc. Stephen B. Solcher Retired CFO BMC Software David L. Magdol President & Chief Investment Officer Jesse E. Morris EVP, Chief Financial Officer & Chief Operating Officer Jason B. Beauvais EVP, General Counsel, Secretary & Chief Compliance Officer Nicholas T. Meserve Managing Director Ryan R. Nelson Vice President & Chief Accounting Officer Main Street Capital Corporation Robert J. Dodd Raymond James (901) 579-4560 Mark Hughes Truist Securities (404) 926-5607 Kenneth S. Lee RBC Capital Markets (212) 905-5995 Mitchel Penn Oppenheimer & Co (212) 667-7136 Bryce Rowe B. Riley Financial (703) 312-1820 Erik Zwick Hovde Group (617) 510-1239 Corporate Headquarters 1300 Post Oak Blvd, 8th Floor Houston, TX 77056 Tel: (713) 350-6000 Fax: (713) 350-6042 Independent Registered Public Accounting Firm Grant Thornton, LLP Houston, TX Corporate Counsel Dechert LLP Washington, D.C. Securities Listing Common Stock - NYSE: MAIN Transfer Agent American Stock Transfer & Trust Co. Tel: (800) 937-5449 www.astfinancial.com NYSE: MAIN MAINST CAPITAL CORPORATION Investor Relation Contacts Dwayne L. Hyzak Chief Executive Officer Jesse E. Morris EVP, Chief Financial Officer & Chief Operating Officer Tel: (713) 350-6000 Ken Dennard Zach Vaughan Dennard Lascar Investor Relations Tel: (713) 529-6600 Management Executive Committee Dwayne L. Hyzak, Chief Executive Officer David L. Magdol, President & Chief Investment Officer Jesse E. Morris, EVP, Chief Financial Officer & Chief Operating Officer Jason B. Beauvais, EVP, General Counsel, Secretary & Chief Compliance Officer Investment Committee Dwayne L. Hyzak, Chief Executive Officer David L. Magdol, President & Chief Investment Officer Vincent D. Foster, Chairman of the Board mainstcapital.com Page 49