Our knowledge of the biology of lizards in the genus Xenosaurus has increased over the past 20 years. Several generalities appear to hold for these lizards; however, some traits appear to vary among populations and species of Xenosaurus. Here we report on the thermal ecology, sexual dimorphism, and diet of a population of the recently described Xenosaurus tzacualtipantecus from Hidalgo, Mexico. The mean body temperature (T_b) of X. tzacualtipantecus in our population (18.1 °C) is the lowest mean T_b yet observed in Xenosaurus. The close relationships between T_b and air temperatures (T_a) suggest that X. tzacualtipantecus is closer to the thermoconformer end of the thermoconformer-thermoregulator continuum. Females of X. tzacualtipantecus had greater snout—vent lengths than males, males had longer femurs than females, and there was no difference in head size between the sexes. Xenosaurus tzacualtipantecus consumes a variety of invertebrates, primarily insects, suggesting that it is an opportunistic or generalist predator. The diets of lizards in the wet season were dominated by caterpillars, whereas in the dry season beetles were more important. Our observations on the ecology and natural history of X. tzacualtipantecus are generally consistent with previous observations on similar traits in other Xenosaurus.