Exhibit 5.1

DLA Piper LLP (US)

51 John F. Kennedy Parkway, Suite 120

Short Hills, New Jersey 07078

www.dlapiper.com

T: 973-520-2550

F: 973-520-2551

Attorneys Responsible for Short Hills Office:

Andrew P. Gilbert

Michael E. Helmer

April 6, 2015

CytoSorbents Corporation

7 Deer Park Drive, Suite K

Monmouth Junction, New Jersey 08852

Re: CytoSorbents Corporation – Registration Statement on Form S-8

Dear Ladies and Gentlemen:

We have acted as counsel to CytoSorbents Corporation, a Delaware corporation (the “Company”), in connection with the preparation of a Registration Statement on Form S-8 (the “Registration Statement”) under the Securities Act of 1933, as amended (the “Act”). The Registration Statement relates to the registration of 2,400,000 shares of the Company’s common stock, par value $0.001 per share (the “Shares”), issuable under the 2014 Long-Term Incentive Plan (the “2014 Long-Term Incentive Plan”).

In connection with this opinion letter, we have examined the Registration Statement and originals, or copies certified or otherwise identified to our satisfaction, of the Articles of Incorporation, as amended and restated, and Bylaws of the Company and such other documents, records and other instruments as we have deemed appropriate for purposes of the opinion set forth herein.

We have assumed the genuineness of all signatures, the legal capacity of all natural persons, the authenticity of the documents submitted to us as originals, the conformity with the originals of all documents submitted to us as certified, facsimile or photostatic copies and the authenticity of the originals of all documents submitted to us as copies.

Based upon the foregoing, we are of the opinion that the Shares have been duly authorized by the Company and, when issued and sold by the Company and delivered by the Company against receipt of the purchase price therefor, in the manner contemplated by the Company’s 2014 Long-Term Incentive Plan will be validly issued, fully paid and non-assessable.

We hereby consent to the use of this opinion as Exhibit 5.1 to the Registration Statement. In giving such consent, we do not hereby admit that we are acting within the category of persons whose consent is required under Section 7 of the Act or the rules or regulations of the Securities and Exchange Commission thereunder.

Very truly yours,

/s/ DLA Piper LLP (US)