Having the same coloration as its pre-evolved form, Houndour, Houndoom has a taller build with a longer snout. There are two white bands at each of Houndoom's ankles instead of just one, as well as three bands on its back instead of two. Houndoom has a long, skinny tail that ends in an arrowhead and visible claws on its feet. It appears to have a collar with a small skull pendant and a pair of curled horns, but no discernible ears.