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UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 10-Q/A

(Amendment No. 1)

For the quarterly period ended June 30, 2013

OR

For the transition period from                      to                     

Commission File Number 001-35243

SUNCOKE ENERGY, INC.

(Exact name of registrant as specified in its charter)

1011 Warrenville Road, Suite 600

Lisle, Illinois 60532

(630) 824-1000

(Registrant’s telephone number, including area code)

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.    x  Yes    ¨  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).    x  Yes    ¨  No

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.

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

As of July 26, 2013, there were 70,001,070 shares of the Registrant’s 0.01 par value Common Stock outstanding.

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SUNCOKE ENERGY, INC.

Form 10-Q/A Amendment No. 1

(September 10, 2013)

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EXPLANATORY NOTE

The registrant filed with the Securities and Exchange Commission (the “SEC”) a Quarterly Report on Form 10-Q for the quarterly period ended June 30, 2013 (“Original Form 10-Q”) on July 30, 2013. However the registrant inadvertently omitted certain required language from paragraph 4 of the certifications of the registrant’s principal executive officer and principal financial officer required by Exchange Act Rule 13a-14(a), as adopted pursuant to Section 302 of the Sarbanes-Oxley Act of 2002.

This Amendment No. 1 on Form 10-Q/A is being filed solely for the purpose of filing revised certifications by the registrant’s principal executive officer and principal financial officer, including the previously omitted language. These revised certifications are currently dated, refer to this Form 10-Q/A, and are being included as exhibits to this Amendment No.1 on Form10-Q/A under Part II, Item 6 hereof. In accordance with interpretation 246.13 in the Regulation S-K section of the SEC’s “Compliance & Disclosure Interpretations,” this Form 10-Q/A contains only the cover page, this explanatory note, a signature page, and the revised certifications (containing only paragraphs 1, 2, 4 and 5 of the text otherwise prescribed by Item 601(b)(31)(i) of Regulation S-K).

Except as described above, no attempt has been made in this Amendment No.1 on Form 10-Q/A to modify or update the other disclosures or exhibits presented in the Original Form 10-Q. Except as presented in this Form 10-Q/A and except for Exhibits 31.1 and 31.2 filed herewith, this Amendment No. 1 on Form 10-Q/A does not reflect events occurring after the filing of the Original Form 10-Q, or modify or update those disclosures. Accordingly, this Amendment No. 1 on Form 10-Q/A should be read in conjunction with the Original Form 10-Q and the registrant’s other filings with the SEC.

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PART IV

Item 6. 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 Amendment No. 1 on Form 10-Q/A report to be signed on its behalf by the undersigned, thereunto duly authorized on this 10th day of September 2013.

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