Mexican agoutis are rabbit-sized rodents with blackish-brown, slightly grizzled pelage. They have rounded backs and long, thin legs adapted for running. The rump is black, the breast is whitish-brown, and parts of the throat and stomach are white. The shoulders and thighs have denser speckling than the sides. The tail is short, black, and hidden under posterior hair. Their body length ranges from 446 to 557 mm, their tail is between 20 to 30 mm, and most adults weigh between 2 and 5 kg.
The head of Mexican agoutis is black on top and brown on its sides with some minor white speckling. Skin surrounding the eyes is pink and sparsely covered with downy gray or brown hair. The mustache is black and hair on the throat is completely white. Ears are pink at the base, naked and rounded at the tips with the posterior margins somewhat notched. Hairs on the body and neck are brownish-black with two white rings. The overlaying of these ringed hairs produces a mottled appearance. Long black hairs form a line from the middle of the head down along the back, which becomes wider towards its posterior end. Hair next to this line is also long and black but has one white ring. Chest hairs are light brown at the base and white at the tips. Abdominal hairs are brown with a white ring and hair posterior to the abdomen but anterior to the pubic region is either white with a gray base or completely white. The outer front legs are black with speckles and the insides are whitish with gray-based, white-tipped hairs. The fore-feet, which have four toes, are black and flecked with white. The hind feet, which have three toes, are also black with thinly scattered white hairs. At the end of each toe is a hoof-like claw.
Dasyprocta mexicana does not closely resemble any sympatric species. However, it could be confused with other species of agoutis. Dasyprocta mexicana is distinguished from other agoutis by differences in coloration.
Little variation exists among individuals. Juveniles are precocial and look like small adults. One dark brown, grizzled specimen from Tabasco may be a hybrid with Dasyprocta punctata, the Central American agouti. There is no description in the literature of sexual dimorphism, seasonal variation in pelage, recognition of sub-species, or intraspecific polymorphisms.
Range mass: 2 to 5 kg.
Range length: 466 to 587 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: sexes alike