A vehicular exterior rearview mirror assembly includes a blind zone indication module that includes a plastic housing having a front end configured for attaching the blind zone indication module at the rear side of the mirror reflective element. When at least one light emitting diode of the blind zone indication module is electrically powered, light emitted by the light emitting diode exits the blind zone indication module via a light-transmitting portion of the front end of the plastic housing of the blind zone indication module. With the blind zone indication module disposed at the mirror reflective element, and with the light-transmitting portion of the front end of the plastic housing juxtaposed with a light-transmitting aperture of the mirror back plate, light emitted by the light emitting diode passes through the mirror reflective element.