Their bodies are greatly compressed, with both eyes on the left side of the head. The caudal fin is separate, and the pectoral fins are rudimentary or entirely absent; none of the fins have spines. The lateral line is straight and well-developed. The family varies considerably in size, from the 6.3 cm of Achiropsetta slavae to the 60 cm length of the armless flounder Neoachiropsetta milfordi.
Most of the species have only recently been discovered, and little is known of their habits.