The members of the genus Cerebratulus are in general dorsoventrally flattened and quite large. Certain species may attain a length of more than 1 m and a width of several centimetres.

The flat head has large lateral slits, and under the outermost tip of the head the proboscis pore usually appears as a small, circular opening. Further back, on the ventral side of the body, the relatively large mouth is visible as a longitudinal incision. The Cerebratulus species are very difficult to identify by means of external characters. They are mainly associated to mud bottoms.