Parasites can significantly influence the health of the host by inhibiting important physiological and behavioral processes. Some factors like body size, age of host, sex, and season can influence parasite load in nature. Mites are ectoparasites that can occur in lizards, possibly having a negative impact on their host. Our goals were to identify the mite that infested the Neotropical lizard Liolaemus pacha and describe its anatomical distribution, evaluate if mite intensity affected lizard mass, assess the relationship between lizard body size and mite intensity, and calculate the prevalence and intensity of mites in these lizards, comparing males and females and the reproductive and non-reproductive seasons. We analyzed preserved specimens and also studied lizards in their natural environment. We performed linear regression analyses between the intensity of mite infestation and snout-vent length and between lizard mass and intensity of mite infestation. To compare the intensity of mite infestation between sex and season, we used the Mann-Whitney Test. The mite was identified as a species of Pterygosoma Peters, 1849 (Prostigmata: Pterygosomidae). Mite infestation was mainly in the ventral area, particularly in the guiar and lateral regions. Lizard body size did not explain the intensity of mite infestation, nor was lizard mass influenced by the intensity of mite infestation. Males in their natural habitat presented, on average, more mites than females, which might be related to differences in behavior. There were no differences between seasons. This study constitutes the second Argentine record of the presence of the ectoparasite Pterygosoma sp. in a Liolaemus species and the first that explores its relation to ecological parameters.