A new species of rattlesnake is described from the upper elevations of Cerro Tancítaro in Michoacán, in the western portion of the Transverse Volcanic Cordillera. This diminutive rattlesnake appears to be most closely related to several species also occurring at high elevations in Mexico and the southwestern United States including Crotalus intermedius, C. pricei, and C. transversus. The Tancítaro  species is most similar to C. transversus, but differs in aspects of lepidosis and color pattern.