The present study was carried out at commercial hatchery lab in private farm. The experiment was extended from 4 November 2020 to the end of January 2021, in order to investigate the effect of in ovo feeding and early access of diet in the hatcher on the physiological performance and immunity of broiler chicks. An experiment was conducted using 540 commercial fertile eggs of Cobb 500. All eggs were obtained from the same breeder flock and were laid within a 24-hour period. For hatching, all fertile eggs were moved to the incubation room and left for at least 12 hours at room temperature. Then, all eggs were set with wide end up in the setting trays and incubated in a forced draft incubator at 99.5 °F (37.8 °C) with a relative humidity of 60%. Eggs were turned every two hours from the 2^nd to 18^th day of incubation. On 18.5^th day of incubation all eggs were In ovo-injected into the air cell by using an automatic needle, and 0.5 mL of the L-arginine with different ratios was injected in a depth of about 15 mm. Treatment groups were randomly distributed into six-treatment groups: the 1^st group (fertile eggs non-injected negative control, T1), the 2^nd group (fertile eggs injected with distilled water positive control, T2), the 3^rd group (fertile eggs injected with 1% L-Arg and have been added 500-gram starter feed in the hatcher, T3),  the 4^rd group (fertile eggs injected with 1% L-Arg, T4), the 5^th group (fertile eggs injected with 3% L-Arg and have been added 500-gram starter feed in the hatcher, T5), the 6^th group (fertile eggs injected with 3% L-Arg, T6).The injection site was disinfected with 70% ethanol before, immediately after the injection and eggs were returned to the incubator to complete the hatching process for 3 days, then chicks were removed from the hatcher to determine hatchability rate. The chicks were then transported to a private farm.