The objective of this study was to know the response of supplementation of Phaleria macrocarpa (PM) to adriamycin-cyclophosphamide (AC) in the treatment of C3H mice with breast cancer. Twenty-four C3H mice, who were successfully inoculated with breast cancer cells, were randomly allocated into 4 groups: without treatment, treated with AC, treated with AC + PM 0.07 mg/d, and treated with AC + PM 0.14 mg/d. The tumor size was measured using millimeter calipers before and 12 weeks after treatment. The tumor, liver, and kidneys were removed and prepared for pathologic examination using imunohistochemistry staining, and the apoptotic index was counted using the terminal deoxynucleotidyl transferase dUTP nick end labeling method. AC reduce the tumor growth significantly (P < 0.001), whereas supplementation of PM, which significantly reduced the tumor growth compared with AC only, was at the 0.14 mg/d dose (P = 0.007). AC increase the apoptotic index significantly (P < 0.001), and supplementation with PM showed that the higher dose increased the apoptotic index. The correlation between the apoptotic index and the diameter of tumor was significantly negative (r = -0.884; P = 0.020). The apoptotic index of the liver and kidney increased significantly in the AC group (P < 0.001 and P = 0.002, respectively); supplementation with PM decreased significantly the high apoptotic index caused by AC. We conclude that PM supplementation has a synergic effect to AC treatment in reducing the tumor growth, by increasing apoptosis, and protects the liver and kidney from damage caused by AC.