The body of sarcastic fringeheads is elongate, slender, and moderately compressed. Their long dorsal fin extends from the rear of the head almost to the rounded caudal fin. Heads are very large, with bluntly rounded snouts and prominent lips. The huge jaw extends back well past the eye and is larger in males than females. These fish have numerous needle-like teeth and wavy, fringe-like appendages called cirri over their eyes.

The color of sarcastic fringeheads is usually brown to gray, often with a red tinge and green or pale blotches. Males can be almost black with the rear of their giant jaw a bright yellow. Usually there are pale spots or patches on the cheeks. The ocelli (eye-like spots) on the spinous dorsal fin of males are metallic blue, surrounded by a golden ring.

Sarcastic fringeheads can reach 30.5 cm (12 in) long, but most individuals are 7.6-29 cm (3-8 in).

These fish are believed to live about 6 years.

Swimming movements in these small fish are rather complex. Many combinations of fin manipulations are used in their frequently erratic movements. Their dorsal and anal fins are long and unbroken and are used together with their pectoral and caudal fins for swimming. Most swimming consists of short, rapid, darting movements, frequently involving quick changes in direction. Long periods of sustained swimming are not part of this species usual movement pattern.Instead of entering a hole or burrow head-first; fringeheads frequently back into it, eliminating the need to turn around.