In the United States, the distribution of the Northern Brook Lamprey includes Illinois, Indiana, Kentucky, Michigan, Missouri, New York, Ohio, Pennyslvania, West Virginia, and Wisconsin. In Canada, this fish occurs in Ontario, southwestern Quebec and southeastern Manitoba, a distribution that comprises two freshwater biogeographic areas: Great Lakes - Upper St. Lawrence and Saskatchewan - Nelson. Specimens have been found in tributaries to lakes Nipissing, Superior, Huron, and Erie, as well as in the Winnipeg, Ottawa and St. Lawrence rivers. The distribution of four other lamprey species overlaps with the Northern Brook Lamprey in Canada.

The Northern Brook Lamprey is distinguishable from other lamprey species within its Canadian range by its comparatively small size, single dorsal fin and its unique teeth patterns. It has an eel-like appearance with smooth, scale-less skin. It has small eyes and teeth, a single, continuous dorsal fin and seven pairs of gill openings. Adults are dark greyish brown on the back and sides, pale grey or silvery white on the belly. Post-spawning colouration becomes slate blue to black on the back and sides, and white or whitish grey on the belly. Pre-spawning females may have an orange-tinted belly, through which the eggs may be visible. Adults can reach 160 mm in length.