Exhibit 99.1

NEWS RELEASE

MAIN STREET CAPITAL ANNOUNCES INCREASE IN

COMMITMENTS UNDER ITS CREDIT FACILITY

TO $235 MILLION

HOUSTON, December 30, 2011 — Main Street Capital Corporation (NYSE: MAIN) (“Main Street”) announced today the expansion of total commitments under its three-year credit facility (the “Credit Facility”) from $210 million to $235 million.  The $25 million increase in total commitments included the addition of one new lender relationship which further diversifies the Main Street lending group to a total of eight participants. The recent increase in total commitments was executed under the accordion feature of the Credit Facility which allows Main Street to increase the total commitments under the facility up to $300 million of total commitments from new or existing lenders on the same terms and conditions as the existing commitments.

The increase in total commitments under the Credit Facility provides Main Street with access to additional financing capacity in support of its future investment and operational activities.  As of today, Main Street has approximately $94 million of outstanding debt under the Credit Facility.

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. Main Street’s lower middle market investments are made to support management buyouts, recapitalizations, growth financings and acquisitions of companies that operate in diverse industry sectors and generally

have annual revenues ranging from $10 million to $100 million.  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 also maintains a portfolio of privately placed, interest-bearing debt investments in middle market businesses that are generally larger in size than its lower middle market portfolio companies.

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