Adult female Steller sea lions are 2.3 m in length and weigh about 300 kg. Pups weigh about 20 kg when born.
Male pups are usually larger than female pups.
When dry, Steller sea lions are a tan to golden-brown colour and darken to a chocolate brown on their flippers and underside. They appear dark brown or black when wet. Male Steller sea lions have a thick mane. To protect themselves from the cold temperatures and from jagged rocks, Steller sea lions have thick coarse fur when dry, and smooth, slick fur that lies flat against the skin when wet. Blubber is their main form of insulation.