Main Street Investor Presentation

MAIN 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 MAINST 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 86% increase in monthly dividends from $0.33 per share paid in Q4 2007 to declared dividends of $0.615 per share for Q4 2020 Owns three Small Business Investment Company (SBIC) Funds Main Street Mezzanine Fund (2002 vintage), Main Street Capital II (2006 vintage) and Main Street Capital III (2016 vintage) + Provides access to 10-year, low cost, fixed rate 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 investment grade rating of BBB-/Stable from Standard & Poor's Rating Services • Total SBIC debenture regulatory financing capacity of $350.0 million Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 5

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