The present study was focused on examining the effect of catechin on the cellular and humoral immunity in rat model. Immunomodulatory effect of catechin was determined by delayed-type hypersensitivity (DTH) response, carbon clearance assay, leucocyte mobilization test and cyclophosphamide-induced myelosuppression and hemagglutinating antibody (HA) titer assay. Catechin in experimental dose (25, 50 and 100 mg/kg, p.o.) elevated a significant increase in antibody titer in the hemagglutination test with increased levels of immunoglobulin. There was an enhancement in the delayed-type hypersensitivity reaction produced by sheep red blood cells. There was also restoration in the functioning of leucocytes in cyclophosphamide-treated rats with an increased clearance of carbon particles. The results of the present study signify that catechin possesses sufficient potential for modulating immune activity by cellular and humoral mechanisms.