The current study aimed at evaluation the effects of in ovo injection of the myostatin inhibitor, myostatin pro-pepetide (MyoPro) gene on growth performance of Fayoumi chicken. A total number of 200 Fayoumi fertilized pure breed eggs were obtained from EL-Tkamoly poultry project - EL-Azab – Fayoum. Eggs were divided into two equal groups. Group 1(control group, n=100) was injected with saline, and group 2 (treated group, n=100) injected with Myo-pro gene. Growth parameters were recorded (body weight, body weight gain, feed consumption per group was measured for calculating feed conversion ratio). The obtained results revealed that injection of myo-pro to Fayoumi eggs resulted in highly significant increase in body weight and weight gain during all experimental period when compared with control group. Feed conversion ratio of Myo-pro injected group was signifantly lower than control group. However, food intake showed no significant change between the two group. From the obtained results, injection of Myo-Pro gene causing marked increase in body weight gain and improvement in feed conversion ratio with out change in feed intake in fayoumi chicken.