Polycera tricolor, commonly known as the three-color polycera,[2] is a species of sea slug, a nudibranch, a shell-less marine gastropod mollusc in the family Polyceridae.

It occurs in the Pacific Northwest, ranging from southern Alaska southward to northern Mexico, at depths down to about 60 m (200 ft).

[3][4] Polycera tricolor is native to the northeastern Pacific Ocean.

Having no shell to protect them from predation, nudibranchs secrete various defensive chemicals from glands on their surface.

[6] In this species, the chemical defences are secreted by glands mostly found in the dorsal papillae, the part of the animal a predator might encounter first.