Main Street Capital Investor Day Presentation Deck

Lead 65.7% Private Loan Strategy - 2022 2023 New Originations Strategy (1), (2) Security Type(1), (2) Portfolio Company Ownership (1), (2) Private Equity Sponsor(³) 96.1% 1st Lien 98.4% O Q Q ($ in millions) $32.3 4.25x $22.4 Club 31.4% Q1 2022 Co-Lead 2.9% $33.2 New Private Loans: Average Net Leverage / Average & Median Adjusted EBITDA 5.40x $33.2 $21.4 Q2 2022 3.14x $15.2 Equity 1.6% NYSE: MAIN $30.8 MAIN ST 2.94x CAPITAL CORPORATION $25.1 $37.1 4.23x Q3 2022 Q4 2022 Avg. EBITDA Median EBITDA Net Leverage (1) Current Private Loan portfolio closed by Main Street's Private Credit group and held in MAIN's investment portfolio as of March 31, 2023 Percentages calculated based on cost as of March 31, 2023 (2) (3) Private Equity Sponsor includes (a) traditional private equity funds managed by a private equity firm and (b) family office or other institutional investors with an investment history and capabilities consistent with a private equity sponsor (4) Owned by an individual(s) or any entity other than a Private Equity Sponsor Main Street Capital Corporation Non Sponsored (4) 3.9% $33.4 Q1 2023 mainstcapital.com

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