Abstract: A cover for a male member truck/trailer electrical plug is disclosed for keeping the plug dry and free from moisture and other corrosive or debilitating substances. The cover includes a hollow body made of a resilient material such as rubber or neopreme. An opening is formed in one side of the body member to enable fitting the cover over the plug. A groove is formed in the interior side wall of the hollow to receive the guide rib which is formed on truck/trailer male plugs. The side of the body member opposite the opening is formed in the shape of a nob to enable grasping thereof to place on and remove the cover from the plug. A small conduit is formed in the plug to extend from the hollow of the body member through the rear wall thereof to allow escape of air when the cover is placed over the plug and the entry of air when the cover is removed from the plug.