We measured body size of individuals from two populations of the southern crested newt, Triturus karelinii, from two localities at different altitudes (7 m, Klaros and 1373 m, Reşadiye) in Turkey. Lines of arrested growth (LAGs) recorded in phalanges were used to estimate the age of juveniles and adults. Females were on average larger than males in Klaros, and males were on average larger than females in Reşadiye. Our results did not follow the Bergmann's rule and developmental temperature-size rule: for both sexes, the individuals of lowland population were larger than the individuals of highland population. Significant differences were found between the populations in terms of mean SVL (snout–vent length). The average age was calculated as 6.14 ± 1.51 and 6.16 ± 1.46 yr in Klaros and 5.30 ± 1.20 and 5.76 ± 1.26 yr in Reşadiye, for males and females respectively. No significant differences were found between the age distributions of the females in both populations. Both sexes from lowland population had age distributions that were similar to their counterparts from highland population. The growth curves for T. karelinii populations were well described in a Von Bertalanffy growth model. K was not significantly different between the sexes. However, SVL_max was significantly larger in females than males in both populations