1. The clinical use of doxorubicin, an effective anticancer drug, is severely hampered by its cardiotoxicity. Berberine, a botanical alkaloid, has been reported to possess cardioprotective and antitumor effects. In this study, we investigated the cardioprotective effect of berberine on doxorubicin-induced cardiotoxicity and the effect of berberine on the metabolism of doxorubicin. 2. Adult male Sprague-Dawley rats were administered doxorubicin in the presence or absence of berberine for 2 weeks. Administration of berberine effectively prevented doxorubicin-induced body weight reduction and mortality in rats. 3. Berberine reduced the activity of myocardial enzymes, including aspartate aminotransferase (AST), creatine kinase (CK), CK isoenzyme (CK-MB) and lactate dehydrogenase (LDH). Echocardiographic examination further demonstrated that berberine effectively ameliorated cardiac dysfunction induced by doxorubicin. 4. Berberine inhibited the metabolism of doxorubicin in the cytoplasm of rat heart and reduced the accumulation of doxorubicinol (a secondary alcohol metabolite of doxorubicin) in heart. 5. These data showed that berberine alleviated the doxorubicin-induced cardiotoxicity in rats via inhibition of the metabolism of doxorubicin and reduced accumulation of doxorubicinol selectively in hearts.