Lumpenopsis fishes have very elongated, eel-like bodies which are laterally compressed with a long head which has an elongated snout. The large eyes are placed high on the head which has no tentacles or cirrhi. There are thin bands of teeth on the jaws and there are vomerine teeth. There are a large number of spines making up the dorsal fin. The pectoral fins are large, their length being greater than half the length of the head. These fishes have pelvic fins which have a single spine and 3 soft rays. The anal fin has 2 spines at its origin and forked soft rays. The dorsal and anal fins touch the base of the caudal fin. The gill membranes have a wide fusion but do not join with the isthmus. They are small fishes, the largest species being L. triocellata which s a maximum published standard length of .
