CRZO Carrizo Oil and Gas Inc

Filed by: Carrizo Oil & Gas, Inc.

(Commission File No.: 000-29187-87)

Pursuant to Rule 425 under the Securities Act of 1933

and deemed filed pursuant to 14a-12

of the Securities Exchange Act of 1934

Subject Company: Carrizo Oil & Gas, Inc.

On July 25, 2019, the President and Chief Executive Officer of Carrizo Oil & Gas, Inc. and the President and Chief Executive Officer of Callon Petroleum Company jointly distributed the following communication to their respective employees:

Dear Callon and Carrizo team members,

Since last week’s announcement of the proposed combination of Callon and Carrizo, our leadership teams have been jointly focused on the next steps to bring together two great companies. Today, we are pleased to report that an Integration Team has been mobilized to coordinate all integration activities. It is important to us that both organizations are well-represented in the integration process, and we are grateful to the Integration Team members (listed below) for their efforts and leadership throughout the coming months.

Together, the Integration Team will work with advisors from Alvarez & Marsal to develop and execute plans for integrating functions, processes and systems for the combined company. In addition, the Steering Committee will have input into creating the combined organization, and we will be communicating with you more about that process as the plans come together.

In the coming weeks some of you may be asked by an Integration Team member to lend your subject matter expertise as part of the integration process, and we are appreciative of your support. However, unless you receive a specific request from the Integration Team, please do not reach out to your counterpart to discuss integration planning. We can all have confidence that the Integration Team is managing all work streams.

We remain excited for the compelling opportunities created by the pending combination and are committed to a thoughtful integration and regular communications. In the interim, please be reminded that Callon and Carrizo continue to operate our day-to-day activities as independent companies. It is essential that we remain focused on continuing to safely and responsibly deliver the results that our shareholders expect.

Thank you for your continued commitment to Callon and Carrizo.

Joe & Chip

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.

Additional Information and Where to Find It

In connection with the proposed transaction, Callon and Carrizo intend to file materials with the Securities and Exchange Commission (the “SEC”), including a Registration Statement on Form S-4 of Callon (the “Registration Statement”) that will include a joint proxy statement of Callon and Carrizo that also constitutes a prospectus of Callon. After the Registration Statement is declared effective by the SEC, Callon and Carrizo intend to mail a definitive proxy statement/prospectus to shareholders of Callon and shareholders of Carrizo. 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 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.

Cautionary Statement Regarding Forward-Looking Information

Certain statements in this communication concerning the proposed transaction, including any statements regarding the expected timetable for completing the proposed transaction, the results, effects, benefits and synergies of the proposed transaction, future opportunities for the combined company, future financial performance and condition, guidance and any other statements regarding Callon’s or Carrizo’s future expectations, beliefs, plans, objectives, financial conditions, assumptions or future events or performance that are not historical facts are “forward-looking” statements based on assumptions currently believed to be valid. Forward-looking statements are all statements other than statements of historical facts. The words “anticipate,” “believe,” “ensure,” “expect,” “if,” “intend,” “estimate,” “probable,” “project,” “forecasts,” “predict,” “outlook,” “aim,” “will,” “could,” “should,” “would,” “potential,” “may,” “might,” “anticipate,” “likely” “plan,” “positioned,” “strategy,” and similar expressions or other words of

similar meaning, and the negatives thereof, are intended to identify forward-looking statements. The forward-looking statements are intended to be subject to the safe harbor provided by Section 27A of the Securities Act of 1933, Section 21E of the Securities Exchange Act of 1934 and the Private Securities Litigation Reform Act of 1995.

These forward-looking statements involve significant risks and uncertainties that could cause actual results to differ materially from those anticipated, including, but not limited to, failure to obtain the required votes of Callon’s stockholders or Carrizo’s shareholders to approve the transaction and related matters; whether any redemption of Carrizo’s preferred stock will be necessary or will occur prior to the closing of the transaction; the risk that a condition to closing of the proposed transaction may not be satisfied, that either party may terminate the merger agreement or that the closing of the proposed transaction might be delayed or not occur at all; potential adverse reactions or changes to business or employee relationships, including those resulting from the announcement or completion of the transaction; the diversion of management time on transaction-related issues; the ultimate timing, outcome and results of integrating the operations of Callon and Carrizo; the effects of the business combination of Callon and Carrizo, including the combined company’s future financial condition, results of operations, strategy and plans; the ability of the combined company to realize anticipated synergies in the timeframe expected or at all; changes in capital markets and the ability of the combined company to finance operations in the manner expected; regulatory approval of the transaction; the effects of commodity prices; and the risks of oil and gas activities. Expectations regarding business outlook, including changes in revenue, pricing, capital expenditures, cash flow generation, strategies for our operations, oil and natural gas market conditions, legal, economic and regulatory conditions, and environmental matters are only forecasts regarding these matters.

Additional factors that could cause results to differ materially from those described above can be found in Callon’s Annual Report on Form 10-K for the year ended December 31, 2018 and in its subsequent Quarterly Report on Form 10-Q for the quarter ended March 31, 2019, each of which is on file with the SEC and available from Callon’s website at www.callon.com under the “Investors” tab, and in other documents Callon files with the SEC, and in Carrizo’s Annual Report on Form 10-K for the year ended December 31, 2018 and in its subsequent Quarterly Report on Form 10-Q for the quarter ended March 31, 2019, each of which is on file with the SEC and available from Carrizo’s website at www.carrizo.com under the “Investor Relations” tab, and in other documents Carrizo files with the SEC.

All forward-looking statements speak only as of the date they are made and are based on information available at that time. Neither Callon nor Carrizo assumes any obligation to update forward-looking statements to reflect circumstances or events that occur after the date the forward-looking statements were made or to reflect the occurrence of unanticipated events except as required by federal securities laws. As forward-looking statements involve significant risks and uncertainties, caution should be exercised against placing undue reliance on such statements.