EXHIBIT 5.1

January 16, 2018

One Stop Systems, Inc.

2235 Enterprise Street #110

Escondido, CA 92029

Re: Registration Statement on Form S-1 (No. 333-222121)

Ladies and Gentlemen:

We have acted as special counsel to One Stop Systems, Inc., a Delaware corporation (the “Company”), in connection with the proposed issuance and sale by the Company and the selling stockholder (the “Selling Stockholder”) identified in the Registration Statement (as defined below) of up to 3,306,250 shares of common stock, $0.0001 par value per share, up to 3,090,625 of which are being offered by the Company (the “Company Shares”) and up to 215,625 of which are being offered by the Selling Stockholder (the “Selling Stockholder Shares” and together with the Company Shares, the “Shares”). The Shares are included in a registration statement on Form S-1 under the Securities Act of 1933, as amended (the “Act”), filed with the Securities and Exchange Commission (the “Commission”) on January 16, 2018 (Registration No. 333-222121) (as amended, the “Registration Statement”). The term “Shares” shall include any additional shares of common stock registered by the Company pursuant to Rule 462(b) under the Act in connection with the offering contemplated by the Registration Statement. This opinion is being furnished in connection with the requirements of Item 601(b)(5) of Regulation S-K under the Act, and no opinion is expressed herein as to any matter pertaining to the contents of the Registration Statement or related Prospectus, other than as expressly stated herein with respect to the issue of the Shares.

As such counsel, we have examined such matters of fact and questions of law as we have considered appropriate for purposes of this letter. With your consent, we have relied upon certificates and other assurances of officers of the Company and others as to factual matters without having independently verified such factual matters. We are opining herein as to the General Corporation Law of the State of Delaware and we express no opinion with respect to any other laws.

January 16, 2018

Page 2

Subject to the foregoing and the other matters set forth herein, it is our opinion that, as of the date hereof:

This opinion is for your benefit in connection with the Registration Statement and may be relied upon by you and by persons entitled to rely upon it pursuant to the applicable provisions of the Act. We consent to your filing this opinion as an exhibit to the Registration Statement and to the reference to our firm in the Prospectus under the heading “Legal Matters.” We further consent to the incorporation by reference of this letter and consent into any registration statement filed pursuant to Rule 462(b) with respect to the Shares. In giving such consent, we do not thereby admit that we are in the category of persons whose consent is required under Section 7 of the Act or the rules and regulations of the Commission thereunder.