An accessory system of a vehicle comprises an accessory module assembly having a mounting portion, a head portion and a rearview mirror assembly. The mounting portion extends generally upward when mounted to an attachment member at a vehicle windshield. The head portion may extend generally horizontally and rearwardly with respect to the vehicle from an upper portion of the mounting portion. The head portion comprises electronic circuitry for at least one accessory. The mirror assembly is mountable to the mounting portion, with the head portion of the accessory module assembly extending generally above the mirror casing. The head portion may be viewable and/or user accessible above the mirror casing when the mirror assembly is mounted to the mounting portion. The head portion may be pivotable or articulatable relative to the base portion of the accessory module assembly.