Abstract: A vehicular exterior rearview mirror system includes an exterior rearview mirror assembly and a mirror reflective element sub-assembly having a mirror reflective element. A display indicator has a light source that is activatable to emit light. The light source is disposed behind the reflective element and light emitted by the light source passes through the reflective element to be viewed by the driver of the vehicle. The display indicator is associated with a blind spot detection system of the vehicle and the light source of the display indicator is activated responsive to sensing by a sensor of the blind spot detection system of an object in a blind spot at a side of the vehicle. During daytime operation of the vehicle and when the light source is activated, the display indicator, as viewed by the driver of the vehicle, has a luminance of at least about 5,000 nits.