Longnose suckers have relatively small scales which in turn gives them more scales (lateral line scale count of greater than 85) along their side than any other species of sucker. This species gets its name from its rather long snout that protrudes well beyond the tip of the upper lip. The lips of the longnose sucker have many small round bumps on them, a feature only shared by the blue sucker. Longnose suckers are distinctly bi-colored, meaning there is a sudden change from a darker colored back to a light white or cream colored underside. Breeding males are very dark colored with a rosy red streak on the upper sides. The dorsal and tail fins are slate gray in color and the rest of the fins are yellow to white. The closely related white sucker differs by having a shorter snout, fewer scales, and lips with ridges rather than round bumps.