Aegle marmelos, belongs to family Rutaceae is generally known as bael fruit. They were evaluated for potential immunomodulatory activity using the in vitro Polymorphonuclear leukocyte function test. Both Methanolic and Ethanolic extract of Aegle marmelos leaves were evaluated for their immunomodulatory activity. In in vivo studies, using rats as the animal model. The extract was tested for hypersensitivity and hemagglutination reactions, using shed red blood cells (SRBC) antigen. The methanol extract exhibited a significant increase in the percentage phagocytosis versus the control. It was noted to exhibit a dose related increase in the hypersensitivity reaction, to the SRBC antigen, at concentration of 100 & 200 mg/kg. It also resulted in a significant increase in the antibody titer value, to SRBC, at doses of 100 and 200 ml/kg in animal studies. The Methanolic extract was found to stimulate cell mediated and antibody mediated immune responses in rats.