Chinstrap penguins are white on the front and throat but have a black back. A thin band of black plumage runs from one side of the head to the other, right below each reddish eye and unites under the bill. Chicks have grey backs and white fronts. The male and female Chinstraps are monomorphic, as are all other penguins, thus make it hard to tell them apart without non-morphological cues. They stand about 72 cm tall and weigh about 3.5 to 5 kg.
Adult weight varies during the year.
When the penguin is in the molting season they gain the most weight and when they are in the brooding period they lose the most. Chinstrap penguins are able to withstand extreme cold due to the insulation provided by their short, densely packed feathers. This in turn forms a waterproof coat. Underneath these feathers, a thick layer of fat or blubber also serves as storage for energy. Chinstrap penguins usually lay two eggs, generally two to four weeks later than other pygoscelid species in the same area.