A radiator grille cover for motor vehicles comprises a base panel composed of a flexible material and has suitable fasteners on the base panel for releasable connection to the radiator grille of a motor vehicle. The base panel has a centrally located air-receiving opening with one or more additional panels superimposed thereon which are sized to at least partially cover the opening in the base panel. The additional panels are in the form of flexible flaps with a center opening of a different size, the opening being symmetrical with respect to air passage through the radiator grille and having fasteners for releasably fastening the additional panels to the base panel. One or more of the flaps may be released from a position overlying the center opening of the base panel and inserted into a storage pocket on the front thereof so as not to require complete removal from the grille.