UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

Form 10-K/A

Amendment No. 1

FOR THE FISCAL YEAR ENDED JANUARY 31, 2010

COMMISSION FILE NUMBER 0 – 13442

MENTOR GRAPHICS CORPORATION

(Exact name of registrant as specified in its charter)

(503) 685-7000

(Registrant’s telephone number, including area code)

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

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

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 Act.    Yes  ¨    No  x

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 during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  ¨    No  ¨

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 twelve 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 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 Registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of this Form 10-K or in any amendment to this 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 the definitions of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check one):

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 was approximately $665,717,203 on July 31, 2009 based upon the last price of the Common Stock on that date reported in The NASDAQ Global Select Market. On March 23, 2010, there were 106,259,681 shares of the Registrant’s Common Stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

EXPLANATORY NOTE

The following information was inadvertently omitted from the Company’s Annual Report on Form 10-K for the fiscal year ended January 31, 2010, as originally filed on March 17, 2010.

A special meeting of Shareholders was held pursuant to notice at 5:00 p.m. Pacific time on December 14, 2009 at our offices in Wilsonville, Oregon to consider and vote upon:

Proposal 1 – To approve an amendment to the Mentor Graphics Corporation 1982 Stock Option Plan to permit a one-time stock option exchange program as described in Mentor Graphics Corporation’s Proxy statement.

The results of the voting on this proposal are as follows:

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.

EXHIBIT INDEX