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                                                                     EXHIBIT 5.1


                         GOODWIN, PROCTER & HOAR  LLP
                              COUNSELLORS AT LAW
                                EXCHANGE PLACE
                       BOSTON, MASSACHUSETTS 02109-2881



                                January 8, 1999



Boston Properties, Inc.
8 Arlington Street
Boston, MA  02116

Ladies and Gentlemen:

  This opinion is furnished in connection with the registration pursuant to the
Securities Act of 1933, as amended (the "Act"), of 250,000 shares (the "Shares")
of Common Stock, par value $ 0.01 per share, (the "Common Stock"), of Boston
Properties, Inc. (the "Company") and interests in the Boston Properties, Inc.
1999 Non-Qualified Employee Stock Purchase Plan (the "Plan") sponsored by the
Company and its subsidiaries which may be issued pursuant to the Plan.

  In connection with rendering this opinion, we have examined the Amended and
Restated Certificate of Incorporation and Amended and Restated Bylaws of the
Company, each as amended to date; such records of the corporate proceedings of
the Company as we deemed material; and such other certificates, receipts,
records and documents as we considered necessary for the purposes of this
opinion.  In our examination, we have assumed the genuineness of all signatures,
the legal capacity of natural persons, the authenticity of all documents
submitted to us as certified, photostatic or facsimile copies, the authenticity
of the originals of such copies and the authenticity of telephonic confirmations
of public officials and others.  As to facts material to our opinion, we have
relied upon certificates or telephonic confirmations of public officials and
certificates, documents, statements and other information of the Company or
representatives or officers thereof.

  We are attorneys admitted to practice in The Commonwealth of Massachusetts.
We express no opinion concerning the laws of any jurisdictions other than the
laws of the United States of America, the laws of The Commonwealth of
Massachusetts, and the Delaware General Corporation Law.

  Based upon the foregoing, we are of the opinion that upon the issuance and
delivery of the Shares in accordance with the Registration Statement and the
Plan, the Shares will be duly authorized, validly issued, fully paid and non-
assessable.

  The foregoing assumes that all requisite steps were taken to comply with the
requirements of the Securities Act and applicable requirements of state laws
regulating the offer and sale of securities.

  We hereby consent to the filing of this opinion as an exhibit to the
Registration Statement and to the reference to us with respect to this opinion
under the heading "Legal Matters" in the Prospectus which is a part of such
Registration Statement. 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.

                                    Very truly yours,

                                    /s/ Goodwin, Procter & Hoar  LLP
                                    --------------------------------
                                    GOODWIN, PROCTER & HOAR  LLP
