A rearview mirror assembly includes a mirror reflective element, a front mirror casing portion configured to receive the mirror reflective element, a rear mirror casing and a mirror backplate. The mirror backplate includes a generally planar attachment portion for attaching at a rear surface of the mirror reflective element and includes a perimeter flange circumscribing a perimeter of the generally planar attachment portion. The perimeter flange is partially received in the rear mirror casing portion and partially received in the front mirror casing portion, and the perimeter flange couples the front and rear mirror casing portions to the mirror backplate.