Document

Filed by: Callon Petroleum Company

Pursuant to Rule 425 under the

Securities Act of 1933

and deemed filed pursuant to 14a-12

under the Securities Exchange Act of 1934

Subject Company: Carrizo Oil & Gas, Inc.

Commission File No.: 000-29187-87

On or about October 24, 2019, the following letter was delivered to certain Callon Petroleum Company shareholders.

October 22, 2019

Dear Shareholder:

We have previously sent to you proxy material for the special meeting of Callon Petroleum Company to be held on November 14, 2019. Your Board of Directors unanimously recommends that shareholders vote FOR all the proposals relating to the proposed merger with Carrizo Oil & Gas, Inc.

Since approval of the merger proposal and charter amendment proposal each require the affirmative vote of the holders of a majority of the Callon’s common stock, your vote is important, no matter how many or how few shares you may own. If you have not already done so, please vote TODAY by telephone, via the internet, or by signing, dating and returning the enclosed proxy card in the postage-paid envelope provided.

Very truly yours,

Joseph C. Gatto, Jr.

President, Chief Executive Officer and Director

REMEMBER:

You can vote your shares by telephone, or via the Internet.

Please follow the easy instructions on the enclosed proxy card.

If you have any questions, or need assistance in voting

your shares, please call our proxy solicitor,

INNISFREE M&A INCORPORATED,

TOLL-FREE at 1-888-750-5834.

No Offer or Solicitation

Communications herein do not constitute an offer to sell or the solicitation of an offer to buy any securities or a solicitation of any vote or approval with respect to the proposed transaction or otherwise, nor shall there be any sale of securities in any jurisdiction in which such offer, solicitation or sale would be unlawful prior to registration or qualification under the securities laws of any such jurisdiction. Communication herein do not constitute a notice of redemption with respect to or an offer to purchase or sell (or the solicitation of an offer to purchase or sell) any preferred stock of Carrizo Oil & Gas, Inc.

Additional Information and Where to Find It

In connection with the proposed transaction, Callon Petroleum Company (“Callon”) has filed, and the Securities and Exchange Commission (the “SEC”) has declared effective, a registration statement on Form S-4 (the “Registration Statement”), which contains a joint proxy statement of Callon and Carrizo that also constitutes a prospectus of Callon. This communication is not a substitute for the joint proxy statement/prospectus or the Registration Statement or for any other document that Callon or Carrizo may file with the SEC and/or send to Callon’s shareholders and/or Carrizo’s shareholders in connection with the proposed transaction. INVESTORS AND SECURITY HOLDERS OF CALLON AND CARRIZO ARE URGED TO READ THE REGISTRATION STATEMENT AND JOINT PROXY STATEMENT/PROSPECTUS, AS EACH MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME, AND OTHER RELEVANT DOCUMENTS FILED BY CALLON AND CARRIZO WITH THE SEC CAREFULLY WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT CALLON, CARRIZO AND THE PROPOSED TRANSACTION.

Investors will be able to obtain free copies of the Registration Statement and joint proxy statement/prospectus, as each may be amended from time to time, and other relevant documents filed by Callon and Carrizo with the SEC (when they become available) through the website maintained by the SEC at www.sec.gov. Copies of documents filed with the SEC by Callon will be available free of charge from Callon’s website at www.callon.com under the “Investors” tab or by contacting Callon’s Investor Relations Department at (281) 589-5200 or IR@callon.com. Copies of documents filed with the SEC by Carrizo will be available free of charge from Carrizo’s website at www.carrizo.com under the “Investor Relations” tab or by contacting Carrizo’s Investor Relations Department at (713) 328-1055 or IR@carrizo.com.

Participants in the Proxy Solicitation

Callon, Carrizo and their respective directors and certain of their executive officers and other members of management and employees may be deemed, under SEC rules, to be participants in the solicitation of proxies from Callon’s shareholders and Carrizo’s shareholders in connection with the proposed transaction. Information regarding the executive officers and directors of Callon is included in its definitive proxy statement for its 2019 annual meeting filed with the SEC on March 27, 2019. Information regarding the executive officers and directors of Carrizo is included in its definitive proxy statement for its 2019 annual meeting filed with the SEC on April 2, 2019. Additional information regarding the persons who may be deemed participants and their direct and indirect interests, by security holdings or otherwise, will be set forth in the Registration Statement and joint proxy statement/prospectus and other materials

when they are filed with the SEC in connection with the proposed transaction. Free copies of these documents may be obtained as described in the paragraphs above.