Experiment was conducted to evaluate the effect of green husk of walnut powder on immune responses, by using 200 broilers. Birds were split into five groups and each group into four sub groups which include 10 birds. The levels of zero, 1, 2, 3 and 4 % powder of green husk of walnut were added to diet of each group. Intramuscular injection of 0.1 mL of the 25% SRBC suspension was performed at 8 and 22 d and the titers of IgG and IgM was determined by haemagglutination test at 21, 28, 35 and 42 d. Blood samples were collected to determine count of red and white blood cells and after that birds were slaughter to evaluate weight of visceral fat and organelles at 42 d. Titer IgM was higher in treated birds with 4 % green husk (2.93) than control (2.12) at 21 d (P<0.05). Titer IgG was higher in treated birds with 4 % green husk (5.5), 3% green husk (5.25) and 2% green husk (4.81) than control (3.68) at 42 d (P<0.05). Ratio of hetrophil to lymphocyte and percentage of heterophil were lower in treated birds with 4 % green husk (0.55 and 33.23 respectively) than control (P<0.05). Percentage of lymphocytes was higher in treated birds with 4 % green husk (59.96) than control (56.87; P<0.05). The highest percentage relative weight of bursa was observed in treated birds with 2 (0.17), 3 (0.17) and 4% green husk (0.16; P<0.05). The percentage relative weight of thymus was higher in treated birds with 3% green husk (0.59) and 4% green husk (0.54) than control (P<0.05). Therefore, supplementation diet with green husk of walnut powder improved function of broiler immune system.