This small-to-medium-sized rattlesnake species can be found on the plateau of Central Mexico. at elevations of 4,500ft (1370m) to 8,500 ft. They occur in a variety of habitats from grasslands to pine-oak forests, rocky lava outcrops, grassy plains and even marshlands. This rather colorful rattlesnake species can be more tan, brown, gray, or white as a background to their distinctive "lancehead" spots. The Mexican lancehead rattlesnake's diet consists almost entirely of mammals. Males have a larger head than females and will eat larger prey as a result.

The scientific name of this species "polystictus" refers to its pattern: "poly" = many, "sticto" = spotted.

The venom composition and feeding behavior between adult and juvenile Mexican lance-headed rattlesnakes is different and changes with maturity--a change known as an ontogenetic shift. Adults of this species will frequently bite-and-release their rodent prey, and their venom is less toxic on average and causes more hemorrhaging. Juvenile Mexican lance-headed rattlesnakes will often bite-and-hold their prey, and their venom is slightly more toxic, consisting of more neurotoxic characteristics.