SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549 

FORM 10-K/A

(Mark One)

For the fiscal year Ended December 31, 2012

or

Commission File Number 0-26850

FIRST DEFIANCE FINANCIAL CORP.

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (419) 782-5015

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

(Title of Class)

Indicate by check mark if the registrant is a well-known seasoned issuer, as defined in Rule 405 of the Securities Act.  Yes ¨    No x

Indicate by check mark if registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Exchange Act. Yes ¨   No x

Indicate by check mark whether the Registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the Registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days.  Yes x    No ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Website, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T (§232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files). Yes x   No ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K (§229.405 of this chapter) is not contained herein, and will not be contained to the best of Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or any amendment to this Form 10-K.  ¨

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

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Exchange Act).    Yes  ¨    No  x

The aggregate market value of the voting stock held by non-affiliates of the Registrant computed by reference to the average bid and ask price of such stock as of June 30, 2012 was approximately $160.6 million

As of February 21, 2013, there were issued and outstanding 9,729,466 shares of the Registrant’s common stock.

Documents Incorporated by Reference: None

Explanatory Note

This Amendment No. 1 on Form 10-K/A (this “Amendment”) is being filed by First Defiance Financial Corp. (“First Defiance” or the “Company”) to amend its Annual Report on Form 10-K for the year ended December 31, 2012, filed with the Securities and Exchange Commission on February 28, 2013 (the “Original Filing”). This Amendment is being filed solely to include Exhibit 23.1, the consent of Crowe Horwath LLP, which was inadvertently omitted from the Original Filing.

Except for the foregoing, the Original Filing remains unchanged. This Amendment does not reflect any events that may have occurred subsequent to the Original Filing of February 28, 2013, nor does it modify or otherwise update in any way the disclosures made in the Original Filing. Accordingly, this Amendment should be read in conjunction with the Original Filing.

PART IV

Item 15. Exhibits, Financial Statement Schedules

(a)(3) The following documents are filed as part of this report:

SIGNATURES

Pursuant to the requirements of Sections 13 or 15(d) 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.