A protective cover for a mooring buoy utilizes a plurality of interconnected buoyant chambers, connected in series and separated by flexible spacers. A plurality of ballast filled chambers are located adjacent to and extend beneath the buoyant chambers. The ends of the cover are configured to be connected by snaps or equivalent attachment devices, to form a circular enclosure. A guide ring is connected to one of the buoyant chambers to allow the cover to be slid from the moored vessel, along mooring lines, and then over the buoy, such that the buoyant chambers remain at the waterline. The deployed cover thus provides protection from impact with the hull of the vessel by the buoy. A retrieval line is provided to withdraw the cover from the buoy and return it to the vessel when the vessel is departing the mooring. Included as well is the method of deploying the protective cover from a moored vessel onto a buoy.