LIMITED POWER OF ATTORNEY

        The undersigned hereby constitutes and appoints Michael Lester, Ryan
Pardo and Dayna Mudge, and each of them individually, with full power of
substitution, as the undersigned's true and lawful attorney-in-fact 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, as amended, or any
                rule or regulation of the SEC;

        (2)     execute for and on behalf of the undersigned, in the
                undersigned's capacity as officer and/or director of LifeStance
                Health Group, Inc. (the "Company"), Forms 3, 4, 5 and any
                Schedules 13D or 13G in accordance with Section 16(a) of the
                Securities Exchange Act of 1934, as amended, and the rules
                thereunder;

        (3)     do and perform any and all acts for and on behalf of the
                undersigned that may be necessary or desirable to complete and
                execute any such Form 3, 4, or 5 or Schedule 13D or 13G,
                complete and execute any amendment or amendments thereto, and
                timely file such form 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 that, in the opinion of each 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 each 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 each
                such attorney-in-fact may approve in each such attorney-in-
                fact's discretion.

        The undersigned hereby grants to each such attorney-in-fact full power
and authority to do and perform 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 each such
attorney-in-fact, or each such attorney-in-fact's 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 each
foregoing attorney-in-fact, in serving in such capacity at the request of the
undersigned, are not assuming, nor is the Company assuming, any of the
undersigned's responsibilities to comply with Section 16 of the Securities
Exchange Act of 1934, as amended.

        This Power of Attorney shall remain in full force and effect until the
undersigned is no longer required to file Forms 3, 4, 5, and any Schedules 13D
or 13G with respect to the undersigned's holdings of and transactions in
securities issued by the Company, unless earlier revoked by the undersigned in a
signed writing delivered to each foregoing attorney-in-fact.

        IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to
be executed as of this 17 day of May, 2021.


                                         /s/ William Miller
                                         -----------------------------
                                         Name: William Miller