SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-K/A

Amendment No. 1

FOR THE FISCAL YEAR ENDED DECEMBER 31, 2012

COMMISSION FILE NUMBER 001-08524

MYERS INDUSTRIES, INC.

(Exact name of registrant as specified in its charter)

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  ¨    No  x

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 (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 the 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 (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.  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 Act).    Yes  ¨    No  x

State the aggregate market value of the voting and non-voting common equity held by non-affiliates computed by reference to the closing sale price on the New York Stock Exchange as of June 30, 2012: $541,754,413

Indicate the number of shares outstanding of registrant’s common stock as of February 22, 2013: 33,439,663 Shares of Common Stock, without par value.

DOCUMENTS INCORPORATED BY REFERENCE:

Portions of the Registrant’s Definitive Proxy Statement for its 2013 Annual Meeting of Stockholders are incorporated by reference in Part III of this Form 10-K.

Explanatory Note

This Amendment No. 1 on Form 10-K/A (the “Amendment”) amends Myers Industries, Inc.’s (the “Company”) Annual Report on Form 10-K for the year ended December 31, 2012, as originally filed with the Securities and Exchange Commission on March 4, 2013 (the “Original Filing”). The Company is filing the Amendment solely to amend Item 15(B) Exhibit Index. No attempt has been made in this Amendment to modify or update other disclosures presented in the Original Filing. This Amendment does not reflect events occurring after the date of the filing of the Original Filing or modify or update disclosures, including the exhibits to the Original Filing, affected by subsequent events.

In addition, as required by Rule 12b-15 under the Securities Exchange Act of 1934, new certifications by our principal executive officer and principal financial officer are filed as exhibits to the Amendment under Item 15 of Part IV hereof.

PART IV

15. (B) Exhibits

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.