POWER OF ATTORNEY

        Known by all those present, that Teresa A. Harris hereby constitutes and
appoints each of Raoul K. Maitra, Steven M. Rivkin, and Brian Gayle as her true
and lawful attorneys-in-fact with respect to Altair Engineering Inc. to:

        (1) prepare, execute in the undersigned's name and on the undersigned's
        behalf, and submit to the U.S. Securities and Exchange Commission (the
        "SEC") a Form ID, including amendments thereto, and any other documents
        necessary or appropriate to obtain codes and passwords enabling the
        undersigned to make electronic filings with the SEC of reports required
        by Section 16(a) of the Securities Exchange Act of 1934 or any rule or
        regulation of the SEC;

        (2) execute for and on behalf of the undersigned, Forms 3, 4 and 5 in
        accordance with 16(a) of the Securities Exchange Act of 1934 and the
        rules thereunder;

        (3) do and perform any and all acts for and on behalf of the undersigned
        which may be necessary or desirable to complete and execute any such
        Forms 3, 4, and 5, complete and execute any amendment or amendments
        thereto, and timely file such from with the SEC and any stock exchange
        or similar authority; and

        (4) take any other action of any type whatsoever in connection with the
        foregoing which, in the opinion of such attorney-in-fact, may be of
        benefit to, in the best interest of, or legally required by, the
        undersigned, it being understood that the documents executed by such
        attorney-in-fact on behalf of the undersigned pursuant to this Power of
        Attorney shall be in such form and shall contain such terms and
        conditions as such attorney-in-fact may approve in such attorney-in-
        fact's discretion.

        The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perfom any and every act and thing whatsoever requisite,
necessary, or proper to be done in the exercise of any of the rights and powers
herein granted, as fully to all intents and purposes as the undersigned might or
could do if personally present, with full power of substitution or revocation,
hereby ratifying and confirming all that such attorney-in-fact, or such
attorney- in-fact's designated substitute or substitutes, shall lawfully do or
cause to be done by virtue of this Power of Attorney and the rights and powers
herein granted. The undersigned acknowledges that the foregoing attorneys-in-
fact, in serving in such capacity at the request of the undersigned, are not
assuming any of the undersigned's responsibilities to comply with Section 16 of
the Securities Exchange Act of 1934, as amended, and the rules thereunder.

        This Power of Attorney shall remain in full force and effect until
revoked by the undersigned in a signed writing delivered to the each foregoing
attorney-in-fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 17th day of October, 2017.

                                        /s/ Teresa A. Harris
                                            --------------------------
                                        Name: Teresa A. Harris

Sworn and subscribed before me on October 17, 2017 by Teresa A. Harris.

/s/ Stephanie M. Roehrig
--------------------------------
Stephanie M. Roehrig, Notary Public
Oakland County, Michigan
My Commission Expires: October 4, 2021
Acting in Oakland County