Male Hooded Mergansers in breeding plumage are striking with their black and white markings and reddish-brown flanks, while females are a more subdued gray-brown with a reddish-brown crest. Both sexes have a fan-shaped crest that can be raised or lowered.

Male Hooded Merganser:
• Head: Black with a large white patch on each side that forms the distinctive "hood" when raised. The crest can be raised or lowered to change the shape of the head.
• Body: Black back, white breast with two black bars on each side, and reddish-brown flanks.
• Other features: Yellow eyes, long, narrow, serrated black bill, and dull yellow legs and feet.

Female Hooded Merganser:
• Head: Brownish-gray with a reddish-brown crest. The crest is smaller and less elaborate than the male's.
• Body: Gray-brown overall, lighter below and darker on the back.
• Other features: Brown eyes, and a bill that is black-edged with orange on the upper mandible and yellow on the lower.