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 15, 2019, Carrizo Oil & Gas, Inc. (“Carrizo”) e-mailed the following letter from the President and Chief Executive Officer of Callon Petroleum Company (“Callon”) to Carrizo’s employees.

To our future team members:

On behalf of my colleagues at Callon, I am writing to share how excited we are to join forces with Carrizo and to provide an early welcome to the Callon team.

I see tremendous value in this transaction and in combining our two organizations. Together, we will be better able to compete in this dynamic space while enhancing shareholder value and achieving our shared corporate goals on an accelerated timeline. We view our combined company as a differentiated investment opportunity that will be even more attractive to the market with sustained double-digit production growth within cash flows.

Importantly, we also look forward to the benefit of adding high quality team members to our already deep bench of talent and further advancing our technical and operational skill sets. We have long respected Carrizo and, through the transaction process, my admiration of the organization that you have built has continued to grow. Callon and Carrizo have a lot in common. Like you, we are Houston-based and have established ourselves as leading E&P operators over the 20+ years that we have both operated as public companies. We also have similar cultures – we are both grounded in strong values and a shared commitment to responsible operations, integrity and a drive to deliver leading results. While we have accomplished so much on our own, I firmly believe that together we will achieve well in excess of what we could have done as individual companies.

Successfully bringing our two companies together will require a thoughtful integration plan, and we will work closely with Carrizo to make the post-closing integration as efficient as possible. To start, my executive team and I plan to visit with your Houston employees tomorrow morning to answer questions about the combination and Callon, and I look forward to meeting and speaking with as many of you as possible. We also plan similar visits with the Dilley and Midland offices in the coming days.

As we move forward together, I want to emphasize that we value Carrizo’s operations and talented employees and look forward to getting to know you better in the coming days. We look forward to a bright future together.

Sincerely,

Joe Gatto

President & Chief Executive Officer

Callon Petroleum Company

No Offer or Solicitation

This communication does 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. This communication does 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 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 stockholders 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 Securities and Exchange Commission (the “SEC”) and send to Callon’s stockholders 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 stockholders 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.