Main Street Investor Presentation

MAIN 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 MAINST CAPITAL CORPORATION Equity investments in LMM portfolio provide both 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 " " NAV growth of $8.00 per share (or 62%) since 2007 Cumulative net realized gains from LMM portfolio investments of $117.1 million ($20.4 million net for the total investment portfolio) since the Initial Public Offering Approximately $2.37 per share in cumulative, pre-tax net unrealized appreciation on LMM portfolio at June 30, 2020 • Realized gains provide taxable income in excess of net investment income and help fund MAIN's dividends Internally managed operating structure provides significant operating leverage Favorable ratio of total operating expenses, excluding interest expense, to average total assets of approximately 1.2% (1) Greater portion of gross portfolio returns are delivered to our shareholders Significant positive impact to Net Investment Income Alignment of interests between MAIN management and our shareholders (1) Based upon the trailing twelve months ended June 30, 2020 Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 6

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