A rearview minor system for a vehicle includes an interior rearview mirror assembly having a mirror mount for attaching the mirror assembly to an attachment element at an interior of a vehicle. The mirror assembly includes a base portion disposed generally at a windshield of the equipped vehicle when the mirror mount is attached to the attachment element at the interior of the equipped vehicle. The mirror assembly includes a video camera disposed at the base portion, and the video camera has, when the interior rearview mirror assembly is normally mounted in the equipped vehicle, a field of view towards the windshield of the equipped vehicle. The base portion of the interior rearview mirror assembly encompasses a rain sensor when the mirror mount of the mirror assembly is attached to the attachment element.