UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant To Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): December 16, 2013

Gevo, Inc.

(Exact Name of Registrant as Specified in Charter)

345 Inverness Drive South, Building C, Suite 310, Englewood, CO 80112

(Address of Principal Executive Offices) (Zip Code)

Registrant’s telephone number, including area code: (303) 858-8358

N/A

(Former Name, or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

Introductory Note

On December 16, 2013, Gevo, Inc. (the “Company”) issued and sold 18,525,000 common stock units, each consisting of one share of the Company’s common stock and a warrant to purchase one share of the Company’s common stock (each a “Warrant”) and, pursuant to the exercise of an over-allotment option granted to the underwriter, issued and sold Warrants to purchase an additional 2,778,750 shares of the Company’s common stock, in a firm commitment underwritten public offering (the “Offering”) pursuant to an effective Registration Statement on Form S-3 (Registration No. 333-187893). The net proceeds from the Offering, after deducting the underwriting discounts and commissions and estimated offering expenses, totaled approximately $22.6 million.

The Company used a portion of the net proceeds from the Offering to repay $5.1 million in outstanding long-term debt obligations. The Company intends to use the remaining net proceeds from the Offering to ramp up startup production and sales at its Luverne, Minn. plant and may also use a portion of the net proceeds from the Offering to fund working capital and for other general corporate purposes, which may include paying down additional long-term debt obligations.

The information set forth in the Introductory Note is incorporated herein by reference.

On December 16, 2013, the Company entered into a common stock unit warrant agreement (the “Warrant Agreement”) with American Stock Transfer & Trust Company, LLC (the “Warrant Agent”), pursuant to which the Warrants will be issued at an exercise price equal to $1.85 per share.

Pursuant to the terms of the Warrant Agreement, the Warrants will generally only be exercisable on a cash basis. However, the Warrants may be exercisable on a cashless basis, if and only if, a registration statement relating to the issuance of the shares underlying the Warrants is not then effective or available. The Warrants will be exercisable during the period commencing from the date of original issuance and ending on December 16, 2018, the expiration date of the Warrants. The Warrants may be exercised by surrendering to the Warrant Agent the warrant certificate evidencing the Warrants to be exercised with the accompanying exercise notice, appropriately completed, duly signed and delivered, together with cash payment of the exercise price, if applicable.

In the event of an extraordinary transaction, as described in the Warrant Agreement and generally including any merger with or into another entity, sale of all or substantially all of our assets, tender offer or exchange offer, or reclassification of our common stock, we or any successor entity shall pay at the holder’s option, exercisable at any time concurrently with or within 30 days after the consummation of the extraordinary transaction, an amount of cash equal to the value of such holder’s Warrants as determined in accordance with the Black Scholes option pricing model and the terms of the Warrant Agreement.

The exercise price and the number and type of securities purchasable upon exercise of the Warrants are subject to adjustment upon certain corporate events, including certain combinations, consolidations, liquidations, mergers, recapitalizations, reclassifications, reorganizations, stock dividends and stock splits, a sale of all or substantially all of our assets and certain other events. The Warrants contain weighted average anti-dilution protection upon the issuance of any common stock, securities convertible into common stock or certain other issuances at a price below the then-existing exercise price of the Warrants, with certain exceptions.

No fractional shares will be issued upon exercise of the Warrants. The Warrants do not confer upon holders any voting or other rights as stockholders of the Company.

The foregoing description of the Warrant Agreement and the transactions contemplated thereby does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Warrant Agreement, a copy of which is attached hereto as Exhibit 4.1, and the terms of which are incorporated herein by reference.

The information set forth in the Introductory Note is incorporated herein by reference.

On December 16, 2013, the Company issued a press release announcing the closing of the Offering and the issuance and sale of 18,525,000 common stock units, at a price to the public of $1.35 per unit. Gevo also issued Warrants to purchase an additional 2,778,750 shares of common stock pursuant to the exercise of an over-allotment option granted to the underwriter. A copy of this press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Additional Information and Where to Find It

A shelf registration statement relating to the common stock units issued in the Offering was filed with the U.S. Securities and Exchange Commission (“SEC”) and is effective. Preliminary and final prospectus supplements describing the terms of the Offering have also been filed with the SEC. Copies of the final prospectus supplement and the accompanying prospectus relating to the securities being offered may be obtained from Piper Jaffray & Co., Attention: Prospectus Department, 800 Nicollet Mall, J12S03, Minneapolis, MN 55402, via telephone at 800-747-3924 or email at prospectus@pjc.com. Electronic copies of the final prospectus supplement and accompanying prospectus are also be available on the SEC’s website at http://www.sec.gov.

Forward-Looking Statements

Certain statements in this Current Report on Form 8-K and in the attached exhibits may constitute “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995. Such statements relate to a variety of matters, including, without limitation, statements regarding the Company’s anticipated proceeds from the Offering, and its use of those proceeds and other statements that are not purely statements of historical fact. These forward-looking statements are made on the basis of the current beliefs, expectations and assumptions of the management of the Company and are subject to significant risks and uncertainty. Factors that could cause actual results to differ materially from those described in the forward-looking statements are set forth in the prospectus supplements for the Offering. Investors are cautioned not to place undue reliance on any such forward-looking statements. All such forward-looking statements speak only as of the date they are made, and the Company undertakes no obligation to update or revise these statements, whether as a result of new information, future events or otherwise.

(d) Exhibits.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Date: December 16, 2013