An exterior rearview mirror system for a vehicle includes an exterior rearview mirror assembly and a unitary indicator module disposed at the exterior rearview mirror assembly. The unitary indicator module includes a plurality of illumination sources disposed behind an at least partially light transmitting portion of the unitary indicator module. Light emitted by any of the illumination sources passes through the at least partially light transmitting portion for viewing by a driver of the equipped vehicle. The unitary indicator module is responsive to a control signal to indicate to the driver of the equipped vehicle a detected presence of another vehicle at least one of alongside the equipped vehicle and rearward of the equipped vehicle. The unitary indicator module is operable to indicate a degree of hazard at least one of alongside the equipped vehicle and rearward of the equipped vehicle.