An interior rearview mirror assembly includes a human machine interface having at least one user actuatable input accessible at a portion of the mirror casing. The user actuatable input provides user input to at least one element of circuitry that is disposed in the mirror casing, the interior rearview mirror assembly and/or an accessory module. The circuitry is associated with at least one of (i) a moisture sensor, (ii) a blower motor, (iii) a cabin air monitoring device that monitors the air within the cabin of the vehicle, (iv) a cabin air monitoring device that monitors the level of carbon monoxide in the air within the cabin of the vehicle, (v) an air intake, (vi) a remote ignition system, (vii) a humidity sensing device, and (viii) a display device disposed behind a transflective mirror reflector of the interior rearview mirror assembly and visible to the driver when displaying information.