EXHIBIT 5.1


                   [Letterhead of Christopher O'Brien, Esq.]


                                 July 12, 2001

Mattel, Inc.
333 Continental Boulevard
El Segundo, California 90245-5012

     Re:  Registration Statement on Form S-B
     ---------------------------------------

Ladies and Gentlemen:

     I am the 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 "1933 Act"), of (i) an aggregate of 3,500,000 shares of the common stock
(the "Shares"), $1.00 par value per share, of the Company, which are to be
offered and sold by the Company pursuant to the Mattel, Inc. Personal Investment
Plan and the Mattel, Inc. Hourly Employee Personal Investment Plan
(collectively, the "Plans") and (ii) the preference share purchase rights of the
Company issuable together with the Shares (the "Rights").

     This opinion is delivered in accordance with the requirements of Item
601(b)(5) of Regulation S-K under the 1933 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 Plans (the "Registration Statement"). Such
Registration Statement is being filed with the Securities and Exchange
Commission (the "Commission") under the 1933 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.

     Based on and subject to the foregoing and subject further to the
assumptions set forth below, I am of the opinion that, (i) with respect to any
Shares that are original issuance securities, the Shares, when offered, sold and
paid for pursuant to the terms and conditions of the Plans, will be validly
issued, fully paid and non-assessable and (ii) when the Rights issuable together
with the Shares to be issued pursuant to the Plans have been issued in
accordance with the Rights Agreement dated February 7, 1992 between the Company
and The First National Bank of Boston, as Rights Agent, as amended (the "Rights
Agreement"), such Rights will be validly issued and will be binding obligations
of the Company entitled to the benefits of the Rights Agreement.

          I express no opinion other than on the laws of the State of California
and the General Corporation Law of the State of Delaware, including statutory
and reported decisional law thereunder, and I express no opinion with respect
to the applicability thereto, or the effect


thereon, of the laws of any other jurisdiction or, in the case of Delaware, any
other laws, or as to any matters of municipal law or the laws of any local
agencies within any state.

     I hereby consent to the filing of this opinion as an exhibit to the
Registration Statement. In giving such consent, I do not thereby admit that I am
in the category of persons whose consent is required under Section 7 of the 1933
Act or the rules and regulations of the Commission thereunder.


                              Very truly yours,


                               /s/ Christopher O'Brien
                              -------------------------------------
                              Christopher O'Brien, Esq.
                              Assistant General Counsel
                              and Assistant Secretary