As filed with the Securities and Exchange Commission on April 1, 2013

Registration No. 333-186912

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

AMENDMENT NO. 2

TO

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

INDEPENDENT BANK GROUP, INC.

(Exact name of registrant as specified in its charter)

1600 Redbud Boulevard, Suite 400

McKinney, Texas 75069-3257

(972) 562-9004

(Address, including zip code and telephone number, including area code, of registrant’s principal executive offices)

Mr. David R. Brooks

Chairman and Chief Executive Officer

1600 Redbud Boulevard, Suite 400

McKinney, Texas 75069-3257

(972) 562-9004

(Name, address, including zip code and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, please check the following box.  ¨

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering.  ¨

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a nonaccelerated filer, or a smaller reporting company. See the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act.

EXPLANATORY NOTE

This Amendment No. 2 to the Registration Statement on Form S-1, as amended (Registration No. 333-186912), of Independent Bank Group, Inc. is filed for the purpose of adding an exhibit to such Registration Statement and amending the Exhibit Index, which is incorporated by reference to “Part II—Item 16—Exhibits and Financial Statement Schedules.” This Amendment No. 2 does not modify any provision of the prospectus constituting Part I or the other Items of Part II of the Registration Statement. Accordingly, the prospectus has not been included in this Amendment No. 2.

PART II—INFORMATION NOT REQUIRED IN PROSPECTUS

The following table sets forth all costs and expenses, other than underwriting discounts and commissions, in connection with the sale of shares of our common stock being registered, all of which will be paid by us. All amounts shown are estimates, except for the SEC registration fee, the FINRA filing fee and the NASDAQ Stock Market listing fee.

Article VI of the Company’s certificate of formation and Article VI of the Company’s bylaws provide that the Company shall indemnify any person made a party to or involved in any threatened, pending or completed action, suit or proceeding (whether civil, criminal, administrative or investigative) by reason of the fact that such person is or was a director or officer of the Company or is or was serving at the request of the Company as a director or officer of another foreign or domestic association, corporation, partnership, joint venture, trust or other entity, or employee benefit plan (whether such action, suit or proceeding is based in whole or in part on the sole or contributory gross or ordinary negligence of such person or otherwise).

Article VII of the Company’s certificate of formation provides that a director of the Company shall not be liable to the Company or its shareholders for monetary damages for an act or omission in the director’s capacity as a director, subject to certain limitations.

In Article VI of the Company’s certificate of formation and Article VI of the Company’s bylaws, the Company makes mandatory for directors and officers the indemnification provided for in Section 8.101 of the Texas Business Organizations Code, which provides that, subject to certain limitations, a corporation may indemnify a governing person, former governing person, or delegate who was, is, or is threatened to be made a respondent in a proceeding to the extent permitted by Section 8.102 of the Texas Business Organizations Code if it is determined in accordance with Section 8.103 of the Texas Business Organizations Code that:

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The Company has entered into indemnification agreements with the members of its board of directors (each an “indemnitee”). Each indemnification agreement requires the Company to indemnify each indemnitee to the fullest extent permitted by the Texas Business Organizations Code and any successor statute thereto when such successor statute becomes applicable to the Company. The Company will also, among other things, make the indemnitee whole for costs in any action to establish indemnitee’s right to indemnification, whether or not wholly successful.

The Company also maintains directors’ and officers’ liability insurance.

The form of Underwriting Agreement to be filed as Exhibit 1.1 hereto obligates the underwriters to indemnify our directors, officers and controlling persons under certain circumstances against certain liabilities under the Securities Act.

The following sets forth information regarding unregistered securities that were sold by the Registrant within the past three years, which information has not been adjusted to give effect to the Company’s 3.2-for-one stock split effective February 22, 2013.

The stock grants and private placements of our common stock and 7% Debentures, each as described above, were deemed exempt from registration under Section 4(2) or its successor 4(a)(2) of the Securities Act, and in certain circumstances, in reliance on Rule 701 promulgated under the Securities Act as transactions pursuant to compensatory benefit plans and contracts relating to compensation. All of the foregoing securities are deemed restricted securities for purposes of the Securities Act. The recipients of securities in the transactions exempt under Section 4(2) or its successor 4(a)(2) of the Securities Act represented their intention to acquire the securities for investment purposes only and not with a view to or for sale in connection with any distribution thereof and appropriate legends were affixed to the stock certificates and instruments issued in such transactions.

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The undersigned registrant hereby undertakes to provide to the underwriters at the closing specified in the underwriting agreement certificates in such denominations and registered in such names as required by the underwriters to permit prompt delivery to each purchaser.

Insofar as indemnification for liabilities arising under the Securities Act may be permitted to directors, officers and controlling persons of the registrant pursuant to the indemnification provisions described herein, or otherwise, the registrant has been advised that in the opinion of the SEC such indemnification is against public policy as expressed in the Securities Act and is, therefore, unenforceable. In the event that a claim for indemnification against such liabilities (other than the payment by the registrant of expenses incurred or paid by a director, officer or controlling person of the registrant in the successful defense of any action, suit or proceeding) is asserted by such director, officer or controlling person in connection with the securities being registered, the registrant will, unless in the opinion of its counsel the matter has been settled by controlling precedent, submit to a court of appropriate jurisdiction the question whether such indemnification by it is against public policy as expressed in the Securities Act and will be governed by the final adjudication of such issue.

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The undersigned registrant hereby undertakes that:

(1) For purposes of determining any liability under the Securities Act, the information omitted from the form of prospectus as filed as part of this registration statement in reliance upon Rule 430A and contained in a form of prospectus filed by the registrant pursuant to Rule 424(b)(1) or (4) or 497(h) under the Securities Act shall be deemed to be part of this registration statement as of the time it was declared effective.

(2) For the purpose of determining any liability under the Securities Act, each post-effective amendment that contains a form of prospectus shall be deemed to be a new registration statement relating to the securities offered therein and the offering of such securities at that time shall be deemed to be the initial bona fide offering thereof.

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SIGNATURES

Pursuant to the requirements of the Securities Act of 1933, the Registrant has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of McKinney, Texas, on April 1, 2013.

Pursuant to the requirements of the Securities Act of 1933, this registration statement has been signed below by the following persons in the capacities and on the dates indicated.

EXHIBIT INDEX