UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 8-K

CURRENT REPORT

Pursuant to Section 13 OR 15(d) of the Securities Exchange Act of 1934

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions (see General Instruction A.2.):

¨ Written communications pursuant to Rule 425 under the Securities Act (17CFR 230.425)

¨ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17CFR 240.14a-12)

¨ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17CFR 240.14d-2b)

¨ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17CFR 240.13e-4c)

Item 5.02 Departure of Directors or Certain Officers; Election of Directors; Appointment of Certain Officers; Compensatory Arrangements of Certain Officers.

At a joint meeting of the boards of directors on July 24, 2013, MainStreet BankShares, Inc. (“MainStreet”) and Franklin Community Bank, N.A. (“Franklin Community Bank”) each appointed Brenda H. Smith, age 53, as President and Chief Executive Officer effective immediately. In addition, MainStreet appointed Mrs. Smith to the board of directors of Franklin Community Bank. Mrs. Smith has served as Acting President/CEO of both entities since December 2012, upon the tragic death of former President and CEO, Larry A. Heaton. Brenda has been the Chief Financial Officer of MainStreet since its inception in 1999 and has twenty-five years of banking experience; therefore, she has been a named executive officer for reporting purposes.

At the same joint meeting on July 24, 2013, Franklin Community Bank appointed Todd S. Hammock, age 51, as Executive Vice President/Senior Lender effective immediately. In his new role, Mr. Hammock will be a named executive officer and has a current annual salary of $112,500. Todd participates in the company 401-K plan, group medical and life insurance, and other immaterial reimbursements applicable to his position. Mr. Hammock is currently a Vice President – Business Lending with Franklin Community Bank, having returned to the bank in October 2012. He was previously a Business Banker for Franklin Community Bank from September 2007 to October 2008. Prior to his current position, he was most recently the City President of SunTrust Bank in Martinsville after his promotion from Business Banking Relationship Manager. He was was employed by SunTrust from September 2011 to October 2012. Prior to his employment at SunTrust, Mr. Hammock was a Commercial Relationship Manager for American National Bank and Trust Company in the Martinsville office, where he was employed from October 2008 to September 2011. Collectively, Mr. Hammock has twenty years of previous commercial banking and retail banking experience.

MainStreet is the bank holding company for Franklin Community Bank.

Item 9.01 Financial Statements and Exhibits

(d) Exhibits. The following exhibit is being furnished pursuant to Item 5.02 above.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Index to Exhibits