Infectious bursal disease (IBD) is one of the factors that weakens the immune system, which causes severe economic damage to the poultry industry. Levamisole hydrochloride as an anti-parasitic drug also has immunogenic effects. This study was aimed to investigate the stimulating and strengthening effects of Levamisole hydrochloride on the immune system of broiler chickens vaccinated against infectious bursal disease. A total of 108 one-day-old chicks (Ross308) were divided into three groups considering 18 chicks in each group. In the first group, oral Levamisole hydrochloride from the first day until the end of the breeding period and in the second group, was administrated simultaneously with the infectious bursal disease vaccine from the 19th day until the end of the breeding period. The third group (control) did not take any medicine. Blood samples were taken from each group on the 29th and 40th days for ELISA test and the percentage of blood lymphocytes. The statistical results showed a significant difference in the effect of Levamisole hydrochloride in the first and second groups compared to the control group (P<0.05). The weight of the cloacal bursa and spleen increased in the study groups compared to the control group at the end of the period. According to the results, it can be concluded that Levamisole hydrochloride can strengthen the immune effect of IBD vaccine. پرونده مقاله