An accessory system for a vehicle includes a bracket configured for adhesive attachment at an in-cabin surface of the vehicle windshield. The bracket includes an attaching portion having an aperture therethrough and includes a pair of attaching arms extending from the attaching portion. An interior rearview mirror assembly has a mounting base that is attached at the attaching portion of the bracket with the bracket adhesively attached at the windshield. With the mounting base attached at the attaching portion, a rain sensor is disposed at the in-cabin surface of the windshield and the aperture of the attaching portion circumscribes the rain sensor. With the bracket adhesively attached at the windshield, a forward camera module is attached at the attaching arms of the bracket and generally at the in-cabin surface of the windshield so that an imager of the forward camera module has a field of view through the windshield.