A lighted exterior mirror assembly includes a housing that houses a reflectance element that is movably positionable by the driver of a vehicle to adjust its rearward field of view when the lighted exterior rearview mirror assembly is attached at a side of the vehicle. A ground illumination lamp is disposed at a portion of the lighted exterior mirror assembly and separate from the reflectance element. The ground illumination lamp is a substantially moisture-impervious unit having an enclosure and a lens that is permanently joined with the enclosure. The ground illumination lamp includes a light source disposed within the enclosure behind the lens and, when the lighted exterior mirror assembly is attached at the side of the vehicle and when the light source is electrically powered, the light source emits light that passes through the lens and illuminates a ground area adjacent the side of the vehicle.