An interior rearview mirror assembly for a vehicle includes a mirror head having a mirror casing and a mirror reflective element, and a mirror mounting structure configured to adjustably mount the mirror head at an interior portion of a vehicle. A receiving portion of the mirror head is configured for receiving a portable self-contained garage door opening module at least partially thereat. The module is operable to wirelessly transmit a radio frequency signal responsive to actuation of a user input of the module. With the module at the receiving portion of the mirror head, the user input is accessible by the vehicle driver. A cover element is configured to detachably attach at the mirror casing at the receiving portion to releasably secure the module at the mirror head, with the module being releasable from the mirror head when the cover element is detached from the mirror casing.