Exhibit 31.2

CERTIFICATIONS

I, Brenda H. Smith, certify that:

1. I have reviewed this annual report on Form 10-K of MainStreet BankShares, Inc.;

2. Based on my knowledge, this annual report does not contain any untrue statement of a material fact or omit to state a material fact necessary to make the statements made, in light of the circumstances
under which such statements were made, not misleading with respect to the period covered by this annual report;

3. Based on my knowledge, the
financial statements, and other financial information included in this annual report, fairly present in all material respects the financial condition, results of operations and cash flows of the registrant as of, and for, the periods presented in
this annual report;

4. The registrants other certifying officers and I are responsible for establishing and maintaining disclosure
controls and procedures (as defined in Exchange Act Rules 13a-15(e) and 15d-15(e) and internal control over financial reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15f)) for the registrant and have:

(a) Designed such disclosure controls and procedures, or caused such disclosure controls and procedures to be designed under our supervision; to ensure
that material information relating to the registrant, including its consolidated subsidiaries, is made known to us by others within those entities, particularly during the period in which this annual report is being prepared;

(b) Designed such internal control over financial reporting, or caused such internal control over financial reporting to be designed under our
supervision, to provide reasonable assurance regarding the reliability of financial reporting and the preparation of financial statements for external purposes in accordance with generally accepted accounting principles;

(c) Evaluated the effectiveness of the registrants disclosure controls and procedures and presented in the report our conclusions about the
effectiveness of the disclosure controls and procedures, as of the end of the period covered by this report based on such evaluation; and

(d
) Disclosed in this annual report any change in the registrants internal control over financial reporting that occurred during the registrants most recent fiscal quarter that has materially affected, or is reasonably likely to materially
affect, the registrants internal control over financial reporting; and

5. The registrants other certifying officers and I have
disclosed, based on our most recent evaluation of internal control over financial reporting, to the registrants auditors and the audit committee of registrants board of directors:

(a) All significant deficiencies and material weaknesses in the design or operation of internal control over financial reporting which are reasonably likely to adversely affect the registrants
ability to record, process, summarize and report financial information; and

(b) Any fraud, whether or not material, that involves management
or other employees who have a significant role in the registrants internal control over financial reporting.

6. This annual report does
not include an attestation report of the Companys registered public accounting firm regarding internal control over financial reporting. Managements report was not subject to attestation by the Companys registered public accounting
firm pursuant to temporary rules of the Securities and Exchange Commission that permit the Company to provide only managements report in this Annual Report.



|               |  |  |  |                                                                     
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|Date: 03/17/11 |  |  |  | /s/ Brenda H. Smith                                                 
|               |  |  |  | Brenda H. Smith                                                     
|               |  |  |  | Executive Vice President
Chief Financial Officer Corporate
Secretary



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