Main Street Capital Investor Presentation Deck

Asset 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

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