Breast cancer is the prime cause for cancer mortality in women worldwide. The importance of diverse natural and dietary agents to reduce the risk of developing breast cancer is well established. Berberine, a natural isoquinoline alkaloid found in many medicinal plants is widely used in traditional Indian and Chinese medicine. Because of its capability to seize the cell cycle and induce apoptosis of numerous malignant cells, berberine has received considerable attention as a potential anticancer agent. In the present study, breast cancer was induced in Sprague Dawley (SD) rats by intragastric administration of 7, 12-dimethylbenz[a]anthracene (DMBA) at a dose of 80mg/kg of body weight. Treatment of berberine (50mg/kg BW) to breast tumor bearing rats was found to be effective against DMBA induced mammary carcinoma. The increased levels of lipid peroxide (malonaldehyde), pro-inflammatory cytokines (IL-1β, IL-6 and TNF-α), enzymatic antioxidants (SOD and CAT), non-enzymatic antioxidants (GSH and vitamin C) and transcription factor NF-κB were decreased significantly by administration of berberine. Furthermore, RT-PCR and western blot analysis showed the down-regulation of NF-κB and PCNA in breast tumors. Histopathological studies validated that berberine is effective against DMBA induced ductal carcinoma & invasive carcinoma. Altogether, these findings demonstrate the preventive role of berberine against DMBA induced mammary carcinoma in SD rats.