KNOW ALL BY THESE PRESENTS, that the undersigned hereby constitutes and
appoints Daniel E. Geffken and Max A. Milbury with full power to act as the
undersigned's true and lawful attorneys-in-fact, with full power of
substitution, to:

   1) execute for and on behalf of the undersigned, in the undersigned's
      capacity as an officer and/or director and/or beneficial owner of ProMIS
      Neurosciences Inc. (the "Company"), the Forms 3, 4 and 5 in accordance
      with Section 16(a) of the Securities Exchange Act of 1934, as amended, and
      the rules thereunder;

   2) 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 form with the United States Securities and Exchange
      Commission and any stock exchange or similar authority; and

   3) 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

   The undersigned hereby grants to the 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 such attorney-in-fact or 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.

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

   IN WITNESS WHEREOF, the undersigned has caused this Power of Attorney to be
executed as of this 27th day of April, 2022.

                                          /s/ Gavin T. Malenfant
                                          Gavin Malenfant
                                          Chief Operating Officer