Abstract: A lockable well cap for capping the upper end of a well casing. A base member, which has an upwardly and inwardly interior surface with tapered upwardly directed serrations formed thereon, frictionally engages a portion of the well casing. The outside surface of the base member has a lock tab which aligns with a lock tab on the cover to receive a locking padlock. The cover also includes pins which contact inclined grooves in the base member when properly engaged. A first fluid impervious gasket is seated between the well casing and the base member, and a second fluid impervious gasket is seated between the base member and the cover, both to provide a watertight and waterproof seal.