A vehicular exterior rearview mirror assembly includes a base portion configured for attachment at an exterior portion of a vehicle, a mirror head having a mirror casing and a mirror reflective element, and an actuator at an end of the base portion. An adapter plate of the actuator is attached at a head mounting plate attached at the mirror casing. The mirror back plate is attached at the head mounting plate. A service recess is at and between the mirror back plate and the head mounting plate and is configured to receive a separating element that imparts a separating force at and between the mirror back plate and the head mounting plate to detach at least a portion of the mirror back plate from the head mounting plate. With at least the portion of the mirror back plate detached, the mirror back plate is detachable from the head mounting plate.