Main Street Investor Presentation

MAINST CAPITAL CORPORATION Middle Market Debt Investment Strategy MAIN maintains a portfolio of debt investments in Middle Market companies Investment Objective Generate cash yield to support MAIN monthly dividend Investments in secured and/or rated debt investments First lien, senior secured debt investments Floating rate debt investments Larger companies than the LMM investment strategy ⚫ Current Middle Market portfolio companies have weighted-average EBITDA of approximately $78.1 million(1) Large and critical portion of U.S. economy Nearly 200,000 domestic Middle Market businesses(2) More relative liquidity than LMM investments 6%-10% targeted gross yields • Weighted-average effective yield(3) of 7.7% (4) Net returns positively impacted by lower overhead requirements and modest use of leverage Floating rate debt investments provide matching with MAIN's floating rate credit facility (1) This calculation excludes two Middle Market portfolio companies as EBITDA is not a meaningful metric for these portfolio companies (2) Source: National Center for The Middle Market; includes number of U.S. domestic businesses with revenues between $10 million and $1 billion (3) 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 (4) Weighted-average effective yield is calculated using the applicable floating interest rate as of June 30, 2020 Main Street Capital Corporation NYSE: MAIN mainstcapital.com Page 12

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