Doxorubicin is one of chemotherapeutic agent widely used in breast cancer treatment, but in high dose doxorubicin gives negative side effect, including vomit, nausea, immune suppression, and cardiac toxicity. This toxicity hopefully could be reduced by combination chemotherapy using natural herbs such as ciplukan herb. This research was conducted to explore cytotoxic activity of single ciplukan herbs ethanolic extract and its combination with doxorubicin on T47D breast cancer cells. Cytotoxic activity of ciplukan herbs ethanolic extract only and its combination with doxorubicin were tested on T47D cells using MTT assay to obtain IC50 value and combination index (CI), respectively. Single extract showed cytotoxic activity on T47D cells with IC50 value of was 160 µg/ml. Thus, combination treatment from ciplukan herbs ethanolic extract and doxorubicin showed synergistic effect (CI<1,0). This effect was reached at concentration of ciplukan herbs ethanolic extract-doxorubicin 80 μg/ml- 2 nM, 80 μg/ml-4 nM, and 80 μg/ml-8 nM. This research indicated that ciplukan herbs ethanolic extract is potential to be applied as co-chemotherapeutic agent in breast cancer therapy.Key word : ciplukan herbs, doxorubicin, co-chemotherapy, T47D cells