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

Date of Report (Date of Earliest Event Reported): February 10, 2015

INTERVEST BANCSHARES CORPORATION

(Exact Name of Registrant as Specified in Charter)

Registrant’s Telephone Number Including Area Code: (212) 218-2800

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. below):

Introductory Note

This Current Report on Form 8-K is being filed in connection with the consummation on February 10, 2015 of the transactions contemplated by the Agreement and Plan of Merger (the “Merger Agreement”) dated as of July 31, 2014, by and among Intervest Bancshares Corporation (the “Registrant”), Intervest National Bank, the Registrant’s wholly-owned bank subsidiary, Bank of the Ozarks, Inc. (“Ozarks”) and Bank of the Ozarks, Ozarks’ wholly-owned bank subsidiary (“Bank of the Ozarks”). Pursuant to the Merger Agreement, on February 10, 2015 (the “Effective Time”), the Registrant merged with and into Ozarks (the “Merger”), with Ozarks as the surviving corporation in the Merger. Immediately following the consummation of the Merger, Intervest National Bank merged with and into Bank of the Ozarks (the “Bank Merger”), with Bank of the Ozarks as the surviving bank in the Bank Merger.

Pursuant to the Merger Agreement, holders of the Registrant’s common stock have a right to receive 0.3014 shares (the “Exchange Ratio”) of the common stock of Ozarks, par value $0.01 per share (the “Ozarks Common Stock”) for each share of the Registrant’s common stock held immediately prior to the Effective Time, with cash to be paid in lieu of fractional shares. There were 22,022,090 shares of the Registrant’s common stock issued and outstanding at the Effective Time.

The foregoing description of the Merger Agreement does not purport to be a complete description and is qualified in its entirety by reference to the full text of the Merger Agreement, a copy of which is filed as Exhibit 2.1 to the Registrant’s Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on July 31, 2014, and is incorporated herein by reference.

On February 10, 2015, the Registrant completed the Merger pursuant to the Merger Agreement. As a result of the Merger, the Registrant’s separate corporate existence ceased and Ozarks continued as the surviving corporation.

In accordance with the Merger Agreement, within three business days after the closing of the Merger, Ozarks is obligated to send former stockholders of the Registrant instructions to exchange their shares of the Registrant for shares of Ozarks Common Stock.

The disclosure set forth in the Introductory Note and item 3.01 is incorporated herein by reference.

In connection with the consummation of the Merger, on February 10, 2015, the Registrant requested that The Nasdaq Stock Market LLC (“Nasdaq”) file a notification on Form 25 with the SEC to request the removal of the Registrant’s common stock from listing on Nasdaq and from registration under Section 12(b) of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). Ozarks, as successor to the Registrant, intends to file with the SEC a certification on Form 15 on behalf of the Registrant requesting the suspension of the Registrant’s reporting obligations under Sections 13 and 15(d) of the Exchange Act.

The disclosure set forth in the Introductory Note and in item 3.01 is incorporated herein by reference.

The disclosure set forth in the Introductory Note and items 2.01 and 3.01 is incorporated herein by reference.

As contemplated by the Merger Agreement, each of the directors of the Registrant resigned as a director of the Registrant, which resignations were effective as of the Effective Time. The Merger Agreement provides that the directors and executive officers of the surviving corporation immediately after the Merger shall be the directors and executive officers of Ozarks immediately prior to the Effective Time.

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 thereunto duly authorized.