An extension cord clamp assembly for detachably securing the ends of extension cords or cables together to prevent accidental disconnection of the plug and socket. The clamp assembly has a pair of spring-loaded, butterfly-type clamps which clamp on the cord ends, the clamps being mounted on a threaded, roughened or serrated rod to thereby hold them against relative displacement. The spring urges the clamps into tight and secure engagement with the rod, but permits ready adjustment along the rod when the butterfly wings of the clamps are squeezed together to release the jaws of the clamps.