The Peruvian endemic Lima Leaf-Toed Gecko (Phyllodactylus sentosus) is a critically endangered species with just a few known localities of occurrence, which are isolated from each other, within Lima City and in the Ica region. During 1 yr, we carried out monthly evaluations to determine the influence of the environmental factors on the size and population dynamics of this species in the Huaca Pucllana, as this area maintains one of the largest populations in Lima. We took body measurements and reproductive data and made a total of 1,924 captures and recaptures. The low catchability during the coldest months caused a population underestimation in which adults fluctuated between 69 and 313 and juveniles between 88 and 351 throughout the year for the study area of 6.07 ha. The catchability increased in the warmest months when the adult population peaked between December and January, whereas the population of juveniles peaked in December and April. We noted sexual dimorphism, the females being 8% longer than males. The reproductive cycle seems more similar to that of other species that inhabit the temperate zones, where females have oviductal eggs in spring and the appearance of young individuals occurs in mid- to late summer when food is abundant. We recommend carrying out one evaluation per year in Huaca Pucllana and in the other localities of occurrence of these geckos during summertime. We also recommend carrying out a management program including the translocation of individuals between Huaca Pucllana and the other four closest localities.