The effect of in ovo injection of olive leaf extract as a growth promoter antibiotic was studied on hatchability, day old chick weight, growth rate, feed conversion ratio, mortality and carcass efficiency. Three hundred and twenty eggs were divided into 4 groups, and injected on day 18. Treatments consisted of: 1- control (no injection). 2- injection of 1 ml of distilled water in air sac (DW), 3- injection of 1 ml olive leaf extract containing 0.75% of oleuropein (OL0.75) in the air sac. 4- Injection of 1 ml of olive leaf extract contain 0.9% of oleuropein (OL0.9) in air sac. No significant differences were observed in hatchability and in day old chick weight in eggs treated with olive leaf extract. OL0.9 treatment resulted in lowest mean live weight (P<0.05). Feed intake was not significantly affected by in ovo injection. The highest feed conversion ratio was observed in OL0.9 treatment during the final rearing period. Mortality was not found to be significantly different. Plucked carcass weight ecreased in eggs injected with 0.9% OL and the weight of bursa of fabricius was decreased in OL0.75 and in OL0.9 treatments (P<0.05). Other carcass parameters were not significantly affected by the treatment. It is concluded that a low dose of olive leaf extract may be recommended to promote egg quality, though more research is needed for further clarification.