Age and size-related life-history traits of animals are influenced by a variety of factors. In connection with climate, the effect of altitude on demographic parameters may differ among different populations of the same species. In the present study, we analyzed how body size and longevity of the Asia Minor Thin-toed Gecko (Mediodactylus heterocercus (Blanford, 1874)) vary along an elevational gradient in Turkey. For this purpose, a total of 138 specimens of the species (52 males, 75 females, and 11 juveniles) from 11 different populations were analyzed. Populations at intermediate altitude had shorter lifespans compared with those at low and high altitudes (marginal environments). Furthermore, adult life expectancy (ESP), which indicates the expected lifespan of individuals having reached sexual maturity, was higher in high-altitude populations (ESP: 6.59 years) than in intermediatealtitude populations (ESP: 5.40 years) and low-altitude populations (ESP: 6.01 years). The results of the study suggest that the body size, but not age, of Asia Minor Thin-toed Geckos increases with altitude.