Knowledge of life history and population demography of threatened amphibians is poor. I used skeletochronology in conjunction with mark–recapture data to examine growth rates, age at maturity, and longevity of the spotted tree frog, Litoria spenceri, a critically endangered Australian species. Ages were reliably determined for 578 individuals across two populations at 335- and 1110-m elevation. Females attained larger body sizes than males and took longer to reach sexual maturity, consistent with most anurans. Males matured at 2 yr and females at 3–4 yr at lower elevations, whereas at higher elevations, males matured at 3–4 yr and females took up to 6 yr to mature, which is slow compared with most anurans. Overall, L. spenceri is long-lived, with a maximum confirmed age of 14 yr. These life history attributes have implications for population dynamics of L. spenceri, which may have markedly different demographic responses to certain threatening processes compared with faster growing, shorter lived species. This study highlights the value and need for more life history and demographic data on threatened species. Generalizations about population demography and dynamics across environmental gradients should be made cautiously.