Baudin's black cockatoo is about 56 cm (22 in) long. It is mostly dark-grey with narrow vague light-grey scalloping, which is produced by narrow pale-grey margins at the tip of dark-grey feathers. It has a crest of short feathers on its head, and it has whitish patches of feathers that cover its ears. Its lateral tail feathers are white with black tips, and the central tail feathers are all black. The irises are dark brown and the legs are brown-grey. Its beak is longer and narrower than that of the closely related and similar Carnaby's black cockatoo.