Main Street Investor Presentation

MAINST CAPITAL CORPORATION Total 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 49% LMM / 27% Private Loan / 17% Middle Market / 7% Other (1) Portfolio investments 177 LMM, Private Loan and Middle Market portfolio companies Average investment size of $13.0 million(2) • . Largest individual portfolio company represents 3.7% (3) of total investment income and 3.0% of total portfolio fair value (most investments are less than 1%) Eleven non-accrual investments, which represent 1.9% of the total investment portfolio at fair value and 6.3% at cost. Weighted-average effective yield(4) of 9.5% Significant diversification Issuer • Industry Transaction type • Geography ⚫ End markets . Vintage (1) Other includes MSC Adviser, LLC, MAIN'S External Investment Manager (2) As of June 30, 2020; based on cost (3) Based upon total investment income for the trailing twelve month period ended June 30, 2020 (4) Weighted-average effective yield 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 19

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