DLBS1425 is a bioactive compound extracted from Phaleria macrocarpa, with anti-proliferative, anti-inflammatory and anti-angiogenic properties against cancer cells. The present study was aimed to assess cardiotoxicity of DLBS1425, compared to the mainstay regimen for breast cancer, 5-fluorouracil:doxorubicin:cyclophosphamide (FAC, given at 500/50/500 mg/m(2)). Treatment with FAC regimen at standard dose resulted in very severe toxicity, so mice had no chance to survive for more than 7 days following initial drug treatment. Furthermore, histological examination on the heart revealed severe muscular damage when mice were given the FAC regimen alone (severe toxicity). FAC as chemotherapeutic regimen exerted high toxicity profile to the cardiovascular cells in this experiment. Meanwhile, treatment with DLBS1425 alone up to a dose equivalent to as high as 300 mg three times daily in human had no hazardous consequences on the heart, hematological feature, as well as general safety. In the cardiovascular cells, DLBS1425 in the presence of FAC regimen (one-eight of the initial dose) gave protection to the cardiac muscle cells as well as other hematological features. Taken together, results of the present study suggest that DLBS1425 is safe when used as adjuvant therapy for breast cancer and may be even protective against cardiac cellular damage produced by chemotherapeutic regimen.