There is provided an adapter plate assembly for mounting a license plate to a connector portion of a vehicle. The assembly includes a rectangular adapter plate having a plurality of spaced-apart protrusions adjacent to respective corners thereof. The protrusions are configured to abut and support the recessed rear of the license plate. The assembly includes a plurality of outer apertures that at least partially extend through the protrusions and align with the outer apertures of the license plate. The assembly includes a plurality of inner apertures extending therethrough. The inner apertures are positioned inwards from the protrusions and align with inner apertures of the connector portion. The assembly includes a plurality of fasteners configured to extend through respective ones of the outer and inner apertures. The license plate couples to the adapter plate and the adapter plate coupling to the connector portion of the vehicle thereby.