The breast and underparts are bright white. Two bold black lines running down the side of the bird separate the white of the breast from the finely vermiculated rufous flanks. The upperparts of the wings are blackish with white striping on the flight feathers. The underparts of the wings are light grey to nearly white. They also have some white striping on the wings.
Males have entirely black bills.
Females and juveniles have some orange coloration at the base of the bill and on the lower mandible. Females have dark brown eyes. The Hooded is the only merganser whose range is entirely restricted to North America. They can be divided into western and eastern populations. Western birds breed from Montana and Oregon north to southern Alaska.