Modulation of immune response is highly relevant in tumor cell destruction. The present study is focused on the effect of amentoflavone, a biflavonoid from Biophytum sensitivum on cell-mediated immune responses in normal and tumor-bearing control animals. Tumor was induced in BALB/c mice by intraperitoneal injection of Ehrlich ascites carcinoma cells. Treatment of amentoflavone significantly enhanced natural killer cell activity in normal (42.8% cell lysis) and tumor bearing animals (48.2% cell lysis) on the fifth day, which was much earlier compared to tumor-bearing control animals (20.2% cell lysis on day 9). Antibody-dependent cellular cytotoxicity was also increased in amentoflavone -treated normal (41% cell lysis on day 9) and tumor bearing animals (43.8% cell lysis on day 9) compared to untreated tumor bearing control animals (maximum of 15.2% cell lysis on day 13). Amentoflavone administration could significantly enhance the mitogen-induced splenocyte, thymocyte, and bone marrow cell proliferation. Treatment of amentoflavone significantly elevated the production of interleukin-2 and interferon-gamma in normal and Ehrlich ascites carcinoma-bearing animals. Moreover amentoflavone treatment significantly reduced the elevated levels of serum sialic acid and serum gamma glutamyl transpeptidase activity in tumor bearing animals.