An exterior rearview mirror assembly for a vehicle includes a mounting portion mountable at a side of a vehicle and a mirror head portion pivotally adjustable relative to the mounting portion. An actuator is operable to impart pivotal movement of the mirror head portion relative to the mounting portion to adjust the mirror head portion relative to the side of the vehicle at which the mounting portion is mounted. The actuator includes a first motor and a second motor operable in tandem to cooperatively drive a common drive gear of a gear system to adjust the mirror head portion relative to the mounting portion. Operation of the first and second motors is synchronized. Operation of the first motor drives a first gear that rotatably drives the common drive gear and operation of the second motor drives a second gear that rotatably drives the common drive gear.