An attempt was made to confirm the earlier reported anticancer activity of Swietenia mahagoni leaf extract (SMLE) in Ehrlich’s ascites carcinoma in mice against 3-methylcholanthrene (3-MC) induced solid tumor in the calf muscle of mice. It was found that SMLE treated groups of mice showed marked reduction in the tumor growth with respect to the corresponding untreated control group of mice. Biochemical studies revealed that SMLE treatment in solid tumor bearing mice causes oxidative stress by the production and accumulation of oxygen free radicals leading to increased intra-metastatic lipid peroxidation which might ultimately lead to loss of integrity of spread tumor cells thus causing the anti-tumor effect