Incubation temperature is one of the most studied factors driving phenotypic plasticity in oviparous reptiles and has been shown to affect a wide variety of traits including body size, shape, and performance. Thermal regimes during embryogenesis might therefore have direct consequences on fitness, potentially even shaping population trajectories. These effects are likely strongest in short-lived species where even temporary temperature-induced differences in body size or shape might have adaptive significance. We investigated the effects of incubation temperature on the body size and shape of hatchling Australian Painted Dragons (Ctenophorus pictus). Eggs incubated at low temperature required a longer incubation period, but produced hatchlings of greater body mass. However, no effect of temperature was found on the structural dimensions of hatchlings. These results might be explained by an increased absorption of water by the developing embryo during the prolonged incubation period. A greater water content might increase early-life desiccation tolerance in this short-lived lizard inhabiting arid and semiarid environments. Egg mass, however, had the strongest effect on hatchling phenotype, with larger eggs producing larger hatchlings. Furthermore, there was a seasonal effect on yolk allocation, with eggs laid earlier being larger than those laid later. Our results indicate that yolk allocation is the most important factor affecting hatchling phenotype in this species, while temperature mainly affects embryo developmental rate and likely has an indirect effect on hatchling water content.