An interior rearview mirror assembly for a vehicle includes a mirror reflective element having at least one transparent or glass substrate and a mirror reflector established at a surface of the at least one transparent or glass substrate. A mirror backplate is disposed to the rear of the mirror reflective element. A mounting base is configured for attachment at an interior portion of a vehicle. The mounting base includes a ball member. A socket element is formed separate from the mirror backplate and the mounting base. The socket element is attachable at the mirror backplate and is configured to pivotally attach to the ball member of the mounting base. With the socket element attached at the mirror backplate, the socket element pivotally attaches to the ball member to pivotally mount the mirror backplate and the mirror reflective element at the mounting base.