A new alligator lizard is described from the Chihuahuan Desert in southwestern Tamaulipas, Mexico. This lizard appears to be most closely related to the smooth-scaled, relatively small-bodied alligator lizards Gerrhonotus lugoi, from the Cuatro Ciénegas Basin of central Coahuila, and G. parvus, from the central part of Nuevo León, but differs from these species, especially G. parvus, in a number of morphological characters. We tentatively place our new species in the genus Gerrhonotus alongside G. lugoi and G. parvus, but concede that future research is needed to ascertain the phylogenetic placement of these smooth-scaled gerrhonotine lizards.