A vehicular exterior rearview mirror assembly includes a mounting arm configured for attachment at a side of a vehicle and a mirror head having a mirror reflective element. With the mounting arm attached at the side of the vehicle, the mirror reflective element is oriented to provide a driver of the vehicle a field of view rearward and sideward of the vehicle when the mirror head is in a retracted position and when the mirror head is in an extended position. With the mounting arm attached at the side of the vehicle, and when the mirror head is moved along the mounting arm, angle of the mirror head relative to the side of the vehicle at which the vehicular exterior rearview mirror assembly is attached adjusts to provide the driver of the vehicle the field of view rearward and sideward of the vehicle.