DELCATH SYSTEMS, INC.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, DC 20549

SCHEDULE 14A

(Rule 14a-101)

INFORMATION REQUIRED IN PROXY STATEMENT

SCHEDULE 14A INFORMATION

Proxy Statement Pursuant to Section 14(a) of the

Securities Exchange Act of 1934

Filed by the Registrantx

Filed by a Party other than the Registranto

Check the appropriate box:

Delcath Systems, Inc.

(Name of Registrant as Specified In Its Charter)

(Name of Person(s) Filing Proxy Statement, if Other Than The Registrant)

Payment of Filing Fee (Check the appropriate box):

NOTICE OF ANNUAL MEETING OF STOCKHOLDERS

TO BE HELD ON MAY 13, 2026

To the Stockholders of Delcath Systems, Inc.:

Notice is hereby given that the 2026 Annual Meeting of Stockholders of Delcath Systems, Inc., a Delaware corporation (the “Company”), will be held virtually at 10:00 a.m. Eastern Time on May 13, 2026 (the “Annual Meeting”). There will not be an option to attend the Annual Meeting at a physical location.

At the Annual Meeting, stockholders of the Company as of the Record Date (as defined below) will be asked to consider and take action on the following proposals:

(1)to elect Elizabeth Czerepak and John R. Sylvester as a Class II directors for a term expiring at the 2029 annual meeting of the Company’s stockholders and until their successors are elected and qualified, or, if sooner, until the director’s death, resignation, retirement, disqualification or removal;

(2)to approve an amendment of the Company’s 2020 Omnibus Equity Incentive Plan to increase by 1,800,000 the number of shares of common stock, $0.01 par value per share (“Common Stock”), available thereunder;

(3)to ratify the selection, by the Audit Committee of our Board of Directors, of CBIZ CPAs P.C. (“CBIZ CPAs”), as the independent registered public accounting firm of the Company for the fiscal year ending December 31, 2026;

(4)to approve, on a non-binding advisory basis, the compensation of our named executive officers as disclosed in the accompanying proxy statement (“Proxy Statement”); and

(5)to transact such other business as may properly come before the Annual Meeting or any adjournments thereof.

The matters listed in this Notice are described in detail in the accompanying Proxy Statement. The Board of Directors is not aware of any other business to come before the Annual Meeting.

Our Board of Directors fixed the close of business on March 16, 2026 as the record date (the “Record Date”) for determining those stockholders who are entitled to notice of and to vote at the Annual Meeting or any adjournment of our Annual Meeting. If you are a stockholder of the Company as of the Record Date, you will be able to attend the Annual Meeting virtually and vote your shares during the Annual Meeting by first registering at https://web.viewproxy.com/DCTH/2026 and entering the 11-digit Virtual Control Number on the Notice of Internet Availability of Proxy Materials, on your proxy card or on the instructions that accompanied your proxy materials. A complete list of registered stockholders entitled to vote at the Annual Meeting will be available for examination by any stockholder for ten days prior to the Annual Meeting for any purposes germane to the Annual Meeting between the hours of 9:00 a.m. and 5:00 p.m., at our principal executive offices at 566 Queensbury Avenue, Queensbury, NY 12804, by contacting the Secretary of the Company.

IMPORTANT NOTICE REGARDING THE AVAILABILITY OF PROXY MATERIALS FOR THE ANNUAL MEETING OF STOCKHOLDERS TO BE HELD ON MAY 13, 2026 AT 10:00 A.M. EASTERN TIME

This Notice, the Proxy Statement and the Company’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025, and any other materials concerning the Annual Meeting, together with any amendments to any of these materials, are available at https://web.viewproxy.com/DCTH/2026. The Proxy Statement is dated April 2, 2026 and is first being made available to stockholders on April 2, 2026.

Your vote is important. You will not be able to attend the Annual Meeting in person. Whether or not you plan to attend the Annual Meeting virtually, please vote over the telephone or via the internet as instructed in Notice of Internet Availability of Proxy Materials or by completing, signing and returning the proxy card mailed to you as promptly as possible to ensure your representation at the Annual Meeting. To ensure that your vote will be counted, you must register at https://web.viewproxy.com/DCTH/2026 by 11:59 p.m. Eastern Time on May 11, 2026. Once registered, please cast your vote before 11:59 p.m. Eastern Time on May 12, 2026. Even if you have voted by proxy, you may still vote online if you attend the Annual Meeting. Stockholders who virtually attend the Annual Meeting should follow the instructions at www.FCRvote.com/DCTH to vote online at the Annual Meeting. Please note, however, that if your shares are held of record by a bank, broker or other nominee and you wish to vote at the Annual Meeting, you must obtain a proxy issued in your name from that record holder.

By order of the Board of Directors,