Commerson's dolphins are mostly white and have black marked faces and bodies. This black and white pattern varies with geographic location as well as age and sex. These colors are more muted in coastal waters. The black color on the head extends behind the blowhole and down the sides of the body, including the flippers. Black also covers the dorsal fin and runs back to encircle the tailstock behind the anus and flukes. The black color on the chest ends in a posterior-facing point. Large black genital patches are oval or heart-shaped, with the narrow end pointing posteriorly in males. In females the narrow end is anterior, and may or may not include "ears" outside the mammary slits. The throat is generally white, as is the rest of the body. Individuals can be recognized by varying shape of the black "widow's peak" behind the blowhole as well as pigmentation on the side of the tailstock. Calves are born dark grey and black with vertical creasing as a result of fetal folding. These folds disappear after a week, and the dark grey portions become paler in the first few months and white within 4 to 6 months.
Coloration of Commerson's dolphins near Kerguelen Island is similiar to that of juveniles from the south Atlantic Ocean. Near Kerguelen, the surface in front of the dorsal fin is grey, as are the sides. The grey behind the blowhole is streaked with black and their "widow's peak" is not as well defined. The white throat patch is more asymmetrical than in individuals from the south Atlantic. Commerson's dolphins near Kerguelen generally have a narrow white line in the center of their chest, a feature seldom found in their counterparts in the south Atlantic Ocean.
Commerson's dolphins have a dark rounded dorsal fin that rises at a shallow angle and flippers with rounded tips. Their head is blunt and has a sloped forehead and little or no beak. A narrow cap extends on the rear half of body from dorsal fin to flukes. The tail flukes are slightly round tipped and notched, and the flippers are small and rounded. The flukes have concave edges with a slight hatch in the middle with dark coloring above and below. Commerson's dolphins have approximately 29 to 30 pairs of pointed teeth in the upper and lower jaws. Newborns range from 0.5 to 0.75 m in length and weigh 4.5 to 7.3 kg. Adults range from 1.2 to 1.5 meters in length and usually weigh 35 to 65 kg. Females are generally larger than males, and Commerson's dolphins from the Indian Ocean tend to be larger than those in the South Atlantic. Also, although Commerson's dolphins from both areas do not have well defined snouts, there is a distinct rostral depression in Kerguelen animals which individuals in the south Atlantic lack.
Range mass: 35 to 65 kg.
Range length: 1.2 to 1.5 m.
Sexual Dimorphism: female larger; sexes colored or patterned differently