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To determine the incubation of ostrich eggs with the effects of egg weight, 544 eggs from ten female African Black ostriches were used in two commercial farm in Sivas and Kayseri provinces of central Anatolia during a laying season. The average weight of eggs in a season was 1552 g. The eggs were evaluated as small, medium and large and the distribution was 54% medium, 24% large and 22% small. The average infertility rate was 22.8% and the differences between the small, medium and large eggs were not significant (P>0.05). The average incubation period was 43.58 days (38-50 days). In terms of incubation period, the differences between the egg size groups were not significant (P>0.05). The average weight loss of eggs during incubation was 13.70% and the differences between the small, medium and large eggs were significant (P<0.01). The average embryonic mortality rate was 19.30%. In terms of embryonic mortality the differences between the small, medium and large eggs were not significant (P>0.05). The average weight of hatched chicks was 1037 g and the differences between small, medium and large eggs were significant (P<0.01). Hatchability of the fertile eggs and the hatchability of the eggs set were 75.00% and 57.90%; While the difference between of fertile eggs between small, medium and large eggs were significant (P<0.05) the differences for the hatchability of egg set were statistically highly significant (P<0.01).