Filed by Hortonworks, Inc.

Pursuant to Rule 425 Under the Securities Act of 1933

And Deemed Filed Pursuant to Rule 14a-12

Under the Securities Exchange Act of 1934

Subject Company: Hortonworks, Inc.

Commission File No. 001-36780

This filing relates to the proposed merger of Hortonworks, Inc., a Delaware corporation (“Hortonworks”), with Surf Merger Corporation (“Merger Sub”), a Delaware corporation and a direct, wholly owned subsidiary of Cloudera, Inc., a Delaware corporation (“Cloudera”), pursuant to the terms of that certain Agreement and Plan of Merger and Reorganization, dated as of October 3, 2018, by and among Hortonworks, Merger Sub and Cloudera.

* * *

All,

Hortonworks’ special meeting of shareholders will be held on December 28, 2018. All employees who hold shares will be able to vote on certain matters related to the closing of the Hortonworks-Cloudera merger.

We ask that all employees who hold shares log their votes via proxy as soon as possible, so we can start getting the vote counts in. Detailed instructions for voting your shares are provided below.

Our Board of Directors recommends that shareholders vote “FOR” the matters being put to vote. The Board’s rationale for these recommendations is set forth in our proxy statement.

Thank you for your continued support of and investment in Hortonworks.

Instructions

To vote electronically, go to proxyvote.com and follow the instructions. You will need a 12-digit control number that is included on your proxy form, which you should have received via email (look for a recent email from E*Trade, with “Special Meeting” in the subject line).

Electronic instructions must be received no later than 11:59 pm ET on December 27, 2018, but we ask that you submit your vote as soon as possible.

You can also transmit your voting instructions by calling 1-800-690-6903.

If you hold shares both in a brokerage account and in your own name, you will receive separate proxy cards to vote those shares. To ensure that all of your shares are voted at the meeting, follow the instructions on each proxy card that you receive.

Please let me know if you have any questions.

Best,

David

Forward-Looking Statements

This communication contains forward-looking statements within the meaning of the federal securities law that are subject to various risks and uncertainties that could cause our actual results to differ materially from those expressed or implied in such statements. Words such as “anticipate,” “expect,” “project,” “intend,” “believe,” and words and terms of similar substance used in connection with any discussion of future plans, actions or events identify forward-looking statements. Such statements are subject to risks and uncertainties that include, but are not limited to: (i) Cloudera or Hortonworks may be unable to obtain stockholder approval as required for the merger; (ii) other conditions to the closing of the merger may not be satisfied; (iii) the merger may involve unexpected costs, liabilities or delays; (iv) the effect of the announcement of the merger on the ability of Cloudera or Hortonworks to retain and hire key personnel and maintain relationships with customers, suppliers and others with whom Cloudera or Hortonworks does business, or on Cloudera’s or Hortonworks’ operating results and business generally; (v) Cloudera’s or Hortonworks’ respective businesses may suffer as a result of uncertainty surrounding the merger and disruption of management’s attention due to the merger; (vi) the outcome of any legal proceedings related to the merger; (vii) Cloudera or Hortonworks may be adversely affected by other economic, business, and/or competitive factors; (viii) the occurrence of any event, change or other circumstances that could give rise to the termination of the merger agreement; (ix) risks that the merger disrupts current plans and operations and the potential difficulties in employee retention as a result of the merger; and (x) other risks to consummation of the merger, including the risk that the merger will not be consummated within the expected time period or at all. Additional factors that may affect the future results of Cloudera and Hortonworks are set forth in their respective filings with the Securities and Exchange Commission (“SEC”), including in a joint proxy statement/prospectus of Cloudera and Hortonworks filed by Cloudera and Hortonworks on November 27, 2018, and each of Cloudera’s and Hortonworks’ most recently filed Annual Report on Form 10-K, subsequent Quarterly Reports on Form 10-Q, Current Reports on Form 8-K and other filings with the SEC, which are available on the SEC’s website at www.sec.gov. See in particular Item 1A of Part II of Cloudera’s Quarterly Report on Form 10-Q for the quarter ended July 31, 2018 under the heading “Risk Factors” and Item 1A of Part II of Hortonworks’ Quarterly Report on Form 10-Q for the quarter ended September 30, 2018 under the heading “Risk Factors.” The risks and uncertainties described above and in the Registration Statement and Cloudera’s most recent Quarterly Report on Form 10-Q and Hortonworks’ most recent Quarterly Report on Form 10-Q are not exclusive and further information concerning Cloudera and Hortonworks and their respective businesses, including factors that potentially could materially affect its business, financial condition or operating results, may emerge from time to time. Readers are urged to consider these factors carefully in evaluating these forward-looking statements. Readers should also carefully review the risk factors described in other documents that Cloudera and Hortonworks file from time to time with the SEC. The forward-looking statements in this communication speak only as of the date of this communication. Except as required by law, Cloudera and Hortonworks assume no obligation to update or revise these forward-looking statements for any reason, even if new information becomes available in the future.

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 merger or otherwise. No offer of securities shall be made except by means of a prospectus meeting the requirements of Section 10 of the Securities Act of 1933, as amended.

Additional Information and Where to Find It

In connection with the proposed merger, Cloudera has filed with the SEC a Registration Statement on Form S-4, (as may be amended from time to time, the “Registration Statement”), which includes a final prospectus with respect to the shares of Cloudera’s common stock to be issued in the proposed merger and a definitive joint proxy statement of Cloudera and Hortonworks with respect to the proposed merger. The Registration Statement was declared effective by the SEC on November 20, 2018 and the definitive joint proxy statement was mailed or otherwise made available to Cloudera’s and Hortonworks’ respective stockholders on November 28, 2018. BEFORE MAKING ANY VOTING DECISION, CLOUDERA’S AND HORTONWORKS’ RESPECTIVE STOCKHOLDERS ARE URGED TO READ THE JOINT PROXY STATEMENT/PROSPECTUS IN ITS ENTIRETY AND ANY OTHER DOCUMENTS FILED BY EACH OF CLOUDERA AND HORTONWORKS WITH THE SEC IN CONNECTION WITH THE PROPOSED MERGER OR INCORPORATED BY REFERENCE THEREIN BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION AND THE PARTIES TO THE PROPOSED TRANSACTION. Investors and security holders can obtain a free copy of the joint proxy statement/prospectus and other documents containing important information about Cloudera and Hortonworks, once such documents are filed with the SEC, through the website maintained by the SEC at www.sec.gov. Cloudera and Hortonworks make available free of charge at www.cloudera.com and www.hortonworks.com, respectively (in the “Investor Relations” section), copies of materials they file with, or furnish to, the SEC. The contents of the websites referenced above are not deemed to be incorporated by reference into the Registration Statement or the joint proxy statement/prospectus.

Participants in the Solicitation

This document does not constitute a solicitation of proxy, an offer to purchase or a solicitation of an offer to sell any securities. Cloudera, Hortonworks and their respective directors, executive officers and certain employees may be deemed to be participants in the solicitation of proxies from the stockholders of Cloudera and Hortonworks in connection with the proposed merger. Information regarding the interests of such individuals in the proposed merger, by security holdings or otherwise, is included in the joint proxy statement/prospectus relating to the proposed merger that has been filed with the SEC. Security holders may also obtain information regarding the names, affiliations and interests of Cloudera’s directors and executive officers in Cloudera’s Annual Report on Form 10-K for the fiscal year ended January 31, 2018, which was filed with the SEC on April 4, 2018, and its definitive proxy statement for the 2018 annual meeting of stockholders, which was filed with the SEC on May 16, 2018. Security holders may obtain information regarding the names, affiliations and interests of Hortonworks’ directors and executive officers in Hortonworks’ Annual Report on Form 10-K for the fiscal year ended December 31, 2017, which was filed with the SEC on March 15, 2018, and its definitive proxy statement for the 2018 annual meeting of stockholders, which was filed with the SEC on April 24, 2018. To the extent the holdings of Cloudera securities by Cloudera’s directors and executive officers or the holdings of Hortonworks securities by Hortonworks’ directors and executive officers have changed since the amounts set forth in Cloudera’s or Hortonworks’ respective proxy statement for its 2018 annual meeting of stockholders, such changes have been or will be reflected on Statements of Change in Ownership on Form 4 filed with the SEC. Additional information regarding the interests of such individuals in the proposed merger are included in the joint proxy statement/prospectus relating to the proposed merger. These documents (when available) may be obtained free of charge from the SEC’s website at www.sec.gov, Cloudera’s website at www.cloudera.com and Hortonworks’ website at www.hortonworks.com. The contents of the websites referenced above are not deemed to be incorporated by reference into the Registration Statement or the joint proxy statement/prospectus.