Heatwaves are a regular occurrence in Australia, and are predicted to increase in intensity and duration in the future. These changes may elevate temperatures inside lizard nests, shortening the incubation period, so that hatchlings are more likely to emerge during heatwaves. Potentially, developmental plasticity or heat hardening could buffer hatchings from future warming. For example, higher incubation temperatures could shift critical thermal maxima upwards, enabling lizards to withstand higher temperatures. To investigate whether developmental plasticity affects hatchling thermal tolerance, we incubated eggs of the velvet gecko Amalosia lesueurii under two fluctuating incubation treatments to mimic current warm (mean = 24.3°C, range 18.4 - 31.1°C) and future hot (mean = 28.9°C, range 19.1 - 38.1°C) nest temperatures. We maintained the hatchlings under identical conditions, and measured their thermal tolerance (CTmax) at age 14 d and 42 d. We then released hatchlings at field sites, and recaptured individually marked lizards at age six months, to determine whether incubation induced shifts in thermal tolerance were transitory or long-lasting. We found that at age 14 d, hatchlings from the future hot temperature incubation treatment had higher CTmax (mean = 39.96 ± 0.25°C) than hatchlings from the current warm incubation treatment (mean = 39.70 ± 0.36°C). Hatchlings from the warm-incubation treatment also had significantly higher heat hardening capacity (mean = 0.79 ± 0.37°C) than hatchlings from hot-temperature incubation treatment (mean = 0.47 ± 0.17°C). However, both of these incubation-induced effects did not persist into later life. By contrast, incubation treatment had significant and long-lasting effects on the cold tolerance of hatchlings. At age 14 d, warm-incubated hatchlings tolerated colder temperatures (CTmin = 11.24 ± 0.41°C) than hot-incubated hatchlings (CTmin = 14.11 ± 0.25°C). This significant difference in cold tolerance persisted into the juvenile life stage, and was present in 6 month old lizards that we recaptured from field sites. This finding indicates that upward shifts in cold tolerance caused by higher nest temperatures might impact negatively on overwinter survival of lizards, but field studies linking fitness to thermal tolerance are necessary to test this idea. Overall, our results suggest that developmental plasticity for heat tolerance is unlikely to buffer lizard populations from increasing temperatures.