The slimy sculpin does not have scales. Some of its other distinguishing traits are the flattened head, slender body and separate dorsal fins. There are usually three pelvic fin rays and small spines on the head and behind the enlarged pectoral fins. The lateral line is generally incomplete. The back is dark-brown, green or gray, and dark-gray blotches are present on the back and upper sides. A large black spot can be seen at each the front and rear edge of the first dorsal fin. These spots may be large enough that they are joined into a bar. The maximum size for this species is about 4.5 inches in length.
The slimy sculpin lives on the rocky bottom of its water body often in very deep areas. Its head shape and large pectoral fins help it to maintain its position on the bottom. It has some ability to change color to match the color of the bottom substrate of its water body. It feeds on aquatic invertebrates, mainly, but may eat small fishes including other sculpins. Sculpins are prey animals for many larger fishes.