SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K/A

(AMENDMENT NO.1)

(Mark One)

For the fiscal year ended December 31, 2010,

or

For the transition period from              to             

Commission file number 0-16125

FASTENAL COMPANY

(Exact name of registrant as specified in its charter)

(507) 454-5374

(Registrant’s telephone number, including area code)

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

Securities registered pursuant to Section 12(g): None

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

Indicate by check mark if the 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 Web site, 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 is not contained herein, and will not be contained, to the best of the registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of the Form 10-K amended by this Form 10-K/A or any amendment to such Form 10-K.  x

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 definition 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 Common Stock held by non-affiliates of the registrant as of June 30, 2010, the last business day of the registrant’s most recently completed second fiscal quarter, was $6,668,887,476, based on the closing sale price of the Common Stock on that date. For purposes of determining this number, all executive officers and directors of the registrant as of June 30, 2010 are considered to be affiliates of the registrant. This number is provided only for the purposes of this report on Form 10-K/A and does not represent an admission by either the registrant or any such person as to the status of such person.

As of February 4, 2011, the registrant had 147,430,712 shares of Common Stock issued and outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of our Proxy Statement for the annual meeting of shareholders to be held Tuesday, April 19, 2011 are incorporated by reference in Part III of this Form 10-K. Portions of our 2010 Annual Report to Shareholders are incorporated by reference in Part II of this Form 10-K.

EXPLANATORY NOTE

We are filing this Amendment No. 1 on Form 10-K/A (this “Amendment”) to our Annual Report on Form 10-K for the year ended December 31, 2010 (the “Original Annual Report”) for the sole purpose of filing Exhibit 13 which was inadvertently omitted from our original filing on February 9, 2011.

Except as described above, we have not modified or updated other disclosures presented in the Original Annual Report. This Amendment does not amend, update or change the financial statements or any other disclosures in the Original Annual Report and does not reflect events occurring after the filing of the Original Annual Report.

PART IV

ITEM 15. EXHIBITS AND FINANCIAL STATEMENT SCHEDULES

SIGNATURES

Pursuant to the requirements of Section 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.

Date: February 10, 2011

INDEX TO EXHIBITS