Change in sex ratios for broiler chickens, has many economic benefits of the poultry industry. The gonads in chick embryo at an early stage have the potential to convert to both sexes (male and female). Sexual differentiation is due to aromatase expression in the left gonad in 5-6 days of the embryonic period and the production of estrogen from testosterone. Administration of aromatase inhibitors prevents the synthesis of estrogen in genetically female birds and produce males with female genotype. In this study, the effects of in ovo injection of 0. 1 mg mushroom extract, nettle extract and fadrozole hydrochloride as aromatase inhibitors on the fifth day of incubation period on hatchability, embryo mortality and performance of hatching chicks were examined. The results of this experiment showed that there were no significant differences in hatchability, embryo mortality during incubation and the weight of hatching chicks. Daily feed intake and body weight gain in chickens hatched from mushroom extract and fadrozole hydrochloride groups were higher than the two other groups (P<0. 05). Also, in ovo injection of a mushroom extract, nettle extract or fadrozole hydrochloride had no effect on the dressing percentage and internal organ weights.