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: March 21, 2017

(Date of earliest event reported)

(Exact name of registrant as specified in its charter)

1400 Woodloch Forest Drive, Suite 300

The Woodlands, Texas 77380

(Address of principal executive offices) (Zip Code)

(281) 298-4246

(Registrant’s telephone number, including area code)

(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:

Item 1.01 Entry into a Material Definitive Agreement.

On March 21, 2017, Earthstone Energy, Inc. (“Earthstone”), Earthstone Energy Holdings, LLC, a Delaware limited liability company (“EEH”), Lynden USA Inc., a Utah corporation (“Lynden”), Lynden USA Operating, LLC, a Texas limited liability company (“Lynden Sub”), Bold Energy Holdings, LLC, a Texas limited liability company (“Bold”), and Bold Energy III LLC, a Texas limited liability company (“Bold Sub”), entered into an amendment (the “Amendment”) to the Contribution Agreement dated November 7, 2016 (the “Contribution Agreement”), among Earthstone, EEH, Lynden, Lynden Sub, Bold and Bold Sub.

The Amendment extends the termination date of the Contribution Agreement from March 31, 2017 to June 30, 2017.

The foregoing summary of the Amendment does not purport to be complete and is subject to, and qualified in its entirety by, the full text of the Amendment, which is attached to this report as Exhibit 2.1 and incorporated herein by reference.

Forward-Looking Statements

This current report contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, as amended. Statements that are not strictly historical statements constitute forward-looking statements and may often, but not always, be identified by the use of such words such as “expects,” “believes,” “intends,” “anticipates,” “plans,” “estimates,” “potential,” “possible,” or “probable” or statements that certain actions, events or results “may,” “will,” “should,” or “could” be taken, occur or be achieved. The forward-looking statements include statements about the expected benefits of the proposed transaction pursuant to the Contribution Agreement (the “Transaction”) to Earthstone and Bold and their stockholders, the anticipated completion of the proposed Transaction or the timing thereof, the expected future reserves, production, financial position, business strategy, revenues, earnings, costs, capital expenditures and debt levels of the combined company, and plans and objectives of management for future operations. Forward-looking statements are based on current expectations and assumptions and analyses made by Earthstone, Bold and their management teams in light of experience and perception of historical trends, current conditions and expected future developments, as well as other factors appropriate under the circumstances. However, whether actual results and developments will conform to expectations is subject to a number of material risks and uncertainties, including but not limited to: the ability to obtain stockholder and regulatory approvals of the proposed Transaction; the ability to complete the proposed Transaction on anticipated terms and timetable; Earthstone’s and Bold’s ability to integrate successfully after the Transaction and achieve anticipated benefits from it; the possibility that various closing conditions for the Transaction may not be satisfied or waived; risks relating to any unforeseen liabilities of Earthstone or Bold; declines in oil, natural gas liquids or natural gas prices; the level of success in exploration, development and production activities; inaccuracies of reserve estimates or assumptions underlying them; revisions to reserve estimates as a result of changes in commodity prices; risks related to level of indebtedness and periodic redeterminations of the borrowing base under Earthstone’s credit agreement; Earthstone’s ability to generate sufficient cash flows from operations to meet the internally funded portion of its capital expenditures budget; Earthstone’s ability to obtain external capital to finance exploration and development operations and acquisitions; the impacts of hedging on results of operations; Earthstone’s ability to replace oil and natural gas reserves; and any loss of senior management or technical personnel. Earthstone’s annual report on Form 10-K for the year ended December 31, 2016, recent current reports on Form 8-K, and other Securities and Exchange Commission (“SEC”) filings discuss some of the important risk factors identified that may affect Earthstone’s business, results of operations, and financial condition. Earthstone undertakes no obligation to revise or update publicly any forward-looking statements except as required by law.

Additional Information and Where to Find It

In connection with the Transaction, Earthstone has filed with the SEC a preliminary proxy statement and will file a definitive proxy statement and other relevant documents in connection with the proposed Transaction. EARTHSTONE URGES INVESTORS AND STOCKHOLDERS TO READ THE DEFINITIVE PROXY STATEMENT AND ANY OTHER RELEVANT DOCUMENTS WHEN THEY BECOME AVAILABLE, BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT EARTHSTONE, BOLD AND THE PROPOSED TRANSACTION. Investors and stockholders will be able to obtain these materials (when they are available) and other documents filed with the SEC free of charge at the SEC’s website, www.sec.gov. In addition, a copy of the definitive proxy statement (when it becomes available) may be obtained free of charge from Earthstone’s website at www.earthstoneenergy.com. Investors and stockholders may also read and copy any reports, statements and other information filed by Earthstone, with the SEC, at the SEC public reference room at 100 F Street, N.E., Washington, D.C. 20549. Please call the SEC at 1-800-SEC-0330 or visit the SEC’s website for further information on its public reference room. In addition, the documents filed with the SEC by Earthstone can be obtained free of charge from Earthstone’s website at www.earthstoneenergy.com or by contacting Earthstone by mail at 1400 Woodloch Forest Drive, Suite 300, The Woodlands, Texas, 77380, or by telephone at (281) 298-4246.

Participants in the Solicitation

Earthstone and its directors, executive officers and certain other members of management and employees may be deemed to be participants in the solicitation of proxies in respect of the proposed Transaction. Information regarding Earthstone’s directors and executive officers is available in its annual report on Form 10-K filed with the SEC by Earthstone on March 15, 2017. Other information regarding the participants in the proxy solicitation and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the proxy statement and other relevant materials to be filed with the SEC when they become available.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

The following exhibit is included with this Current Report on Form 8-K:

SIGNATURE

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.

EXHIBIT INDEX