Jul 7, 2017

Main Street Announces New Portfolio Investment HOUSTON, July 6, 2017-- Main Street Capital Corporation (NYSE: MAIN) ("Main Street") is pleased to announce that it recently made a new portfolio investment in Boccella Precast, LLC ("Boccella" or the "Company"), a manufacturer of structural precast concrete products. Main Street, along with a co-investor, partnered with the Company's management team and Ashland Capital Partners, a Chicago-based private investment firm, to facilitate the transaction, with Main Street funding $18.6 million in a combination of first-lien, senior secured term debt and a direct equity investment. In addition, Main Street and its co-investor are providing Boccella an undrawn credit facility to support its working capital needs. Headquartered in Berlin, New Jersey, and founded in 1969, Boccella is a leading manufacturer of structural precast concrete products for a client base predominantly located in the Northeast and Mid-Atlantic regions of the United States, with a focus on the New York City market. The Company's products are used in a variety of applications including the construction of affordable housing, dormitories, apartment buildings, condominiums, hotels and educational facilities. ABOUT MAIN STREET CAPITAL CORPORATION Main Street (www.mainstcapital.com) is a principal investment firm that primarily provides long-term debt and equity capital to lower middle market companies and debt capital to middle market companies. Main Street's portfolio investments are typically made to support management buyouts, recapitalizations, growth financings, refinancings and acquisitions of companies that operate in diverse industry sectors. Main Street seeks to partner with entrepreneurs, business owners and management teams and generally provides "one stop" financing alternatives within its lower middle market portfolio. Main Street's lower middle market companies generally have annual revenues between $10 million and $150 million. Main Street's middle market debt investments are made in businesses that are generally larger in size than its lower middle market portfolio companies. Main Street's common stock trades on the New York Stock Exchange ("NYSE") under the symbol "MAIN." In addition, Main Street has outstanding 6.125% Notes due 2023, which trade on the NYSE under the symbol "MSCA." Contact: Dwayne L. Hyzak, President & COO, dhyzak@mainstcapital.com Brent D. Smith, CFO, bsmith@mainstcapital.com 713-350-6000