The Mexican kingsnake is a smooth-skinned, slender, sub-cylindrical snake which is more flattened ventrally than most members of the genus Lampropeltis. It has a wide head, large eyes and a long tail. Adults grow to a length of about 140–200 cm (55–79 in). This snake has broad red saddle-shaped markings, bordered with black and separated by cream, brown or pinkish bars. The sequence of colors does not vary but the proportions and shades of the color bands are quite variable. The nominate subspecies has distinctive red markings and intricate patterning on its head. The species is known for sexual dichromatism, with the males being slightly more vividly colored than the females.