EX-5.1

EXHIBIT 5.1

Letterhead of Tiffani L. Magri, Esq.

July 17, 2020

Mattel, Inc.

333 Continental Boulevard

El Segundo, California 90245-5012

Re: Registration Statement on Form S-8

Ladies and Gentlemen:

I am Senior Vice President, Assistant General Counsel and Assistant Secretary of Mattel, Inc., a Delaware corporation (the “Company”). I am delivering this opinion in connection with the registration under the Securities Act of 1933, as amended (the “Securities Act”), of 10,500,000 shares of common stock, par value $1.00 per share of the Company (“Shares”), which are to be offered and sold by the Company pursuant to the Mattel, Inc. Amended and Restated 2010 Equity and Long-Term Compensation Plan (the “2010 Plan”), as amended by the First Amendment to the 2010 Plan, the Second Amendment to the 2010 Plan, the Third Amendment to the 2010 Plan, and the Fourth Amendment to the 2010 Plan (collectively, the “Amended 2010 Plan”).

This opinion is delivered in accordance with the requirements of Item 601(b)(5) of Regulation S-K under the Securities Act in connection with the Registration Statement on Form S-8 that relates to the proposed issuance and sale of the Shares pursuant to the Amended 2010 Plan (the “Registration Statement”). Such Registration Statement is being filed with the Securities and Exchange Commission (the “Commission”) under the Securities Act.

In rendering the opinion set forth herein, I have made such investigations of fact and law, and examined such documents and instruments, or copies thereof established to my satisfaction to be true and correct copies thereof, as I have deemed necessary under the circumstances. In some instances, I have relied upon other attorneys in the Company’s Law Department.

Subject to the foregoing and in reliance thereon, I am of the opinion that, upon the issuance and sale of the Shares in accordance with the terms of the Amended 2010 Plan, assuming in each case that the individual issuances, grants or awards under the Amended 2010 Plan are duly authorized by all necessary corporate action and duly issued, granted or awarded and exercised in accordance with the requirements of law and the Amended 2010 Plan (and the agreements and awards duly adopted thereunder and in accordance therewith), including, without limitation, receipt of legal consideration in excess of the par value of the Shares issued and, when the Shares shall have been duly registered on the books of the transfer agent and registrar therefor in the name or on behalf of the purchasers or when certificates representing the Shares have been manually signed by an authorized officer of the transfer agent and registrar therefor, the issue and sale of the Shares will have been duly authorized by all necessary corporate action of the Company and the Shares will be validly issued, fully paid and nonassessable securities of the Company. In rendering the foregoing opinion, I have assumed that the Company will comply with all applicable notice requirements regarding uncertificated shares provided in the General Corporation Law of the State of Delaware (“DGCL”).