This is a medium-sized dolphin that averages 3 m in length and 300 kg in weight. Maximum size is about 4.3 m in length and 680 kg in weight. Body form is stocky from the dorsal fin forward but the tailstock is slender. The head is blunt, beakless, and divided medially by a heavy crease.
Coloration is dark gray with lighter gray patches ventrally.
In older individuals the face and area just forward of the dorsal fin is also light gray. They are often heavily scarred by parasites and by wounds inflicted by other Risso's dolphins. The blunt, creased head and extensive scarring are noticeable as the animals ride boat bow waves, or spyhop, and are probably the best field character for distinguishing these dolphins. Stranded specimens are distinguished by the unique head shape and crease, and by the teeth. There are up to seven teeth in each side of the lower jaw and none in the upper jaw.