Infectious bursal disease (IBD) is a viral disease of poultry causing immuno-suppression in young chicks. The present project was designed to evaluate the efficacy of two immunostimulants Mentofin and ASI-Mirus against IBDV vaccine. A total 300 broiler chicks were taken, divided in to six groups each having 50 birds and were replicated under controlled conditions. Birds of groups A, B and D were vaccinated with the IBD live virus vaccine. Birds of groups B and C were treated with Mentofin. In group B chicks were treated with Mentofin and group E were supplemented with ASI-MIRUS while F group served as negative control. The effect of immunostimulants on humoral immune response was evaluated by recording weekly serum antibody titer against IBDV through Enzyme linked immunosorbent assay (ELISA). The antibody titer was significantly increased (P<0.05) in group D supplemented with ASI-MIRUS as compared to group B supplemented with Mentofin and vaccinated. Significantly high bursa to body weight ratio was observed in vaccinated group D. Eucalyptus and peppermint oils increases bursa to body weight (B/BW) ratio as compared to untreated groups. In group B (Mentofin treated), bursal samples showed necrosis at medullary region of bursal follicles. Group D (ASI-MIRUS treated) showed the active follicle consist of lymphoid cells and shown no histopathological lesions. These results indicated volatile oils in ASI-MIRUS have effective immunomodulatory effects on humoral immune response against IBD virus in broiler chicks.