AbstractThe sea otter is associated with a cold, marine habitat, has no insulating fat layer, and relies on its fur layer for insulation. Soiled pelage provides inadequate insulation and can lead to hypothermia and death. Information on sea otter pelage, the surface and bound lipids found in the pelage, and histology of the integument is thus relevant to the development of rehabilitation and management techniques for sea otters soiled with oil. We present detailed data on the sea otter pelage and integument, including hair bundle density (737–2,465 bundles per cm2), hair density per bundle (19–91.1), total hair density (26,413–164,662 hairs per cm2), guardhair length (8.2–26.9 mm), underfur length (4.6–15.8 mm), guardhair diameter (44.0–106.0 μ), underfur diameter (7.6–11.9 μ), angle of hair with respect to the skin (61.9°‐ 84.3°) and structure of individual hairs as seen with a scanning electron microscope. The hydrocarbon squalene was found to be the major component of the lipids associated with the pelage. Various layers of skin from eight sites on a single animal are described histologically. With the exception of density of the hair coat, sea otter integument is similar to that of