An exterior rearview mirror system for a vehicle includes an exterior rearview mirror assembly having a mounting portion mountable at a side of a vehicle and a mirror head portion pivotally adjustable relative to the mounting portion. The mirror assembly includes an actuator 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 that are operable in tandem to cooperatively rotatably drive a gear to cause the mirror head portion to pivot relative to the mounting portion. Operation of the first motor is synchronized with operation of the second motor.