This medium-sized rattlesnake is unique to Isla San Esteban in the Gulf of California. It was previously considered a subspecies of the black-tailed Rattlesnake (Crotalus molossus) but was elevated to full species status in 1999.

It thrives in xeric thornscrub and rocky hillsides on the island. This species avoids the heat of the day, and becomes active at dusk into early night, except in the cooler months.

Isla San Esteban rattlesnakes are considered stable in terms of conservation, despite occupying such a limited geographic space. There is little to no human activity on the island to hurt them, no invasive predators, and weather events pose no threat to their habitat.