Amphibians are in decline in many parts of the world. Understanding the population dynamics of amphibian species is an important prerequisite for developing effective conservation strategies. We used capture–mark–recapture and skeletochronological techniques to investigate population size, body size, and age structure of metamorphic and pedomorphic forms of Ommatotriton ophryticus between 2006 and 2009 in the northwestern Black Sea region of Turkey. Our findings showed that time-specific survival rate, constant capture probability, no temporary emigration, and time-specific population size were the most appropriate models for this population. According to the best model (Model 6), population size of metamorphic forms of O. ophryticus was estimated as 517 (95% confidence interval [CI] = 338–851) adults in 2006, 338 (95% CI = 282−421) adults in 2008, and 527 (95% CI = 443–646) adults in 2009. Average annual capture probability was estimated at 0.21, although average survival rate across years was 0.35. The mean body size and age structure of the pedomorphs and metamorphs was significantly different for both sexes. Also, body size of both forms of O. ophryticus showed positive significant correlations with age. In addition to this, both forms shared a common allometric slope of the snout–vent lengths vs. age, and older individuals had larger bodies. Moreover, age at first reproduction and longevity exhibited great differences between forms whereas the median age was 4 yr for each newt category, except for metamorphosed males, in which it was 5 yr. These results indicate that pedomorphs in this population show retardation of the somatic development and an earlier maturation.