Common chameleon eggs spend the first months of incubation at low temperatures. I incubated eggs of different clutches at 25°C in four treatments with respectively 0, 84, 119 and 149 days of initial cold period (at 14°C). Treatments with longer cold periods had longer total incubation but shorter periods of incubation at 25°C. Eggs which did not experience initial cold period showed low synchronization at hatching. Hatchling body mass and length were influenced by the length of the cold period. Hatchlings were largest and heaviest for cold periods of intermediate length which had similar duration than the cold period experienced by eggs in nature. These results suggest that the cold torpor period of Common chameleon embryos contributes to optimization of development and growth, and synchronizes hatching.