This species occurs in the Columbia, Flathead, Similkameen and Kettle rivers as well as some of their tributary streams in British Columbia and the adjacent United States. Populations are not overly abundant but seem to be near natural historical levels in the Similkameen River. Only a small portion of the Kettle River in Canada is suitable and populations there are stable but are probably supported by populations in the adjacent portion of the river in the United States. In the Columbia River, populations are low and are very threatened because of hydroelectric dams and reservoirs. The Columbia Mottled Sculpin is generally known from rocky riffle habitats in rivers and streams, but may sometimes occur in lakes as well.

The Columbia Mottled Sculpin is a small fish that reaches a maximum 10 to 11 cm in length. It is a typically shaped sculpin with dark mottling on the fins, tail and body. They begin breeding at about two years of age. Females reach maturity when as small as 55mm long, but most individuals become mature when about 75 mm long. Males are generally bigger than females.