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): April 7, 2015 (April 2, 2015)

Ener-Core, Inc.

(Exact name of registrant as specified in its charter)

(949) 616-3300

(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:

As previously reported in our Current Report on Form 8-K dated April 22, 2014, the registrant completed the sale and issuance of senior secured convertible promissory notes for an aggregate principal amount of $4,575,000 (the “April 2014 Notes”) and warrants for the purchase of up to an aggregate of 4,097,015 shares of our common stock (the “April 2014 Warrants”) to five accredited investors (collectively, the “April 2014 Investors”) on April 16, 2014 (such financing, hereinafter the “April 2014 Financing”). As previously reported in our Current Report on Form 8-K dated August 15, 2014, all of the April 2014 Notes were cancelled following their conversion and redemption pursuant to that certain Conversion and Redemption Agreement dated August 14, 2014 by and among the registrant and the April 2014 Investors. On April 2, 2015, the registrant entered into warrant exchange agreements (the “Exchange Agreement”) with each of the April 2014 Investors in connection with their April 2014 Warrants (the “Warrant Exchange”). In the Exchange Agreements, the April 2014 Investors collectively agreed to surrender for cancellation all of their April 2014 Warrants (which collectively entitled them to purchase an aggregate of 4,097,015 shares of our common stock) in exchange, the registrant will issue to them an aggregate 3,687,316 shares of our common stock (the “Exchange Shares”), which is approximately 90% of the total number of common stock shares that the April 2014 Investors would have been entitled to acquire from the registrant under the terms of the April 2014 Warrants.

In addition, the registrant and the April 2014 Investors agreed that upon delivery of the Exchange Shares, the Securities Purchase Agreement, the April 2014 Warrants, the Registration Rights Agreement, the Pledge and Security Agreement and each of the other agreements entered into in connection with the April 2014 Financing by the registrant and the April 2014 Investors, shall all be terminated and cancelled in full. The registrant also granted the April 2014 Investors a right of first refusal to participate in any future sale of the registrant’s equity or equity equivalent securities on a pro rata basis up to 50% of the securities offered in such sale, from the closing date until April 16, 2016 except for a registered underwritten public offering. In the event that the registrant engages in a registered underwritten public offering of its common stock and the offering price per share in such registered offering is more than 85% of the closing sale price of the registrant’s common stock on the date of pricing of such offering, then the participation right shall be 20% of the securities offered in such registered offering. The transactions contemplated by the Exchange Agreement are subject to the customary closing conditions.

The Exchange Shares, when issued, shall be subject to lock-up restrictions under Lock-Up Agreements separately entered into by and among registrant and the April 2014 Investors. Per the Lock-Up Agreements, the April 2014 Investors agreed that they will not, among other things, offer, sell, contract to sell, hypothecate or otherwise dispose of the Exchange Shares until the earlier of (i) the sixtieth (60th) calendar day following the closing date of Warrant Exchange and (ii) the first date that the weighted average price of the registrant’s common stock equals or exceeds $0.30 (as adjusted for any stock split, stock dividend, stock combination, reclassification or similar transaction occurring after the closing of the Warrant Exchange) for each of ten (10) consecutive trading days.