The Cape Barren Goose is 75-100 cm (30-40 in) long, weighs 3.1-6.8 kg (7-15 lbs) and has a 150-190 cm (59-75 in) wingspan; males are somewhat larger than females. This bird feeds by grazing and rarely swims. It is gregarious outside the breeding season, when it wanders more widely, forming small flocks.
C. novaehollandiae, nesting

It is a most peculiar goose of uncertain affiliations (Sraml et al. 1996). It may either belong into the "true geese" and swan subfamily Anserinae or into the shelduck subfamily Tadorninae as distinct tribe Cereopsini, or be separated, possibly including the prehistorically extinct flightless New Zealand Geese of the genus Cnemiornis, in a distinct subfamily Cereopsinae. Indeed, the first bones of the New Zealand birds to be discovered were similar enough to those of the Cape Barren Goose to erroneously refer to them as "New Zealand Cape Barren Goose" ("Cereopsis" novaezeelandiae).

A previous decline in numbers appears to have been reversed as birds in the east at least have adapted to feeding on agricultural land. The breeding areas are grassy islands off the Australian coast, where this species nests on the ground in colonies. It bears captivity well, quite readily breeding in confinement if large enough paddocks are provided.

In Australia, 19th century explorers named a number of islands "Goose Island" due to the species' presence there.

The smaller population of Cape Barren Goose in Western Australia is described as a subspecies, Cereopsis novaehollandiae grisea, and named for the group of islands known as the Recherche Archipelago.