T HIS study aimed to evaluate the impact of sodium butyrate (SB) on immune response of broiler vaccinated with 2 different inactivated H9N2 vaccines. 150 day-old chicks were divided into 5 groups (every 30 chicks): groups A and B were vaccinated with classical inactivated avian influenza H9N2 vaccine at 1 day-old/ S.C. Group A left without treatment but group B was treated with SB with a dosage of 1g/L of drinking water daily till end of trail. Whereas groups C and D were vaccinated with a developed inactivated avian influenza H9N2P vaccine at the same age S.C. Group C was left without treatment but group D was treated with SB as group B, finally, group E was control group. The results showed no significant effect of SB on level interferon γ in treated and/or vaccinated groups. Significant effect on Abs level with SB supplementation was detected at 14 days in group D in comparison with other groups, then at 35 days SB and or developed H9N2 vaccine revealed an elevation in Abs titer in group B, C, and D respectively by ELISA and HI tests. The significant difference occurred in RW of bursa with group B in comparison with group D and E at 21 and 28 days. Finally, group B showed a significant increase in weight gain at 35 days followed by group D in comparison with other groups. We concluded that supplemented SB at 1gm/ L has a positive impact on both humoral immunity and weight gain of broiler.