Salamandra salamandra has an unusual mode of reproduction. Females retain eggs in their oviducts and give birth to aquatic larvae or, in some populations, to fully metamorphosed juveniles. We investigated how variation in the birth size of larvae of five different sibships of S. salamandra affected larval survival, larval growth rates, time to metamorphosis, and size at metamorphosis under different food and temperature conditions. Maternal effects, via the effect of larval birth size, attenuated throughout development in all environments but still affected metamorphic traits at lower temperatures. Larval developmental time was negatively correlated with larval birth size and positively correlated with size at metamorphosis. After controlling for the effect of larval birth size, broad-sense heritabilities were obtained for residual values of metamorphic traits, indicating that enough genetic variability exists at lower temperature environments and that responses to selection of metamorphic traits are possible. The size at and the time to metamorphosis were phenotypically and genetically correlated. Since both traits presumably affect fitness, genetic dependence between size and time to metamorphosis may act as a constraint on adaptive evolution through antagonistic pleiotropy. Mass-specific growth, time to metamorphosis, and size at metamorphosis were plastic under different temperature and food conditions, but no significant sibship × environment interaction was found for any trait. In addition, significant cross-environment correlation for size at metamorphosis with respect to the food gradient indicates low potential for the adaptive evolution of reaction norms to heterogeneous food environments.