BACKGROUND: Breast cancer is the most commonly diagnosed cancer in women. One in eight women will be diagnosed with breast cancer in their lifetime. Chemotherapy works on active cells. Active cells are cells that are growing and dividing into more of the same type of cell. Cancer cells are active, but so are some healthy cells. Also, scientists work constantly to develop ways of providing treatment with fewer chemotherapy side effects. Objectives: The aim of this study was antitumor effect of simultaneous low-intensity, 150 kHz ultrasound, in combination with the reduced dose of anticancer drug Doxorubicin (DOX) on breast adenocarcinoma using murine model (BALB/c). Methods: Twenty-five female BALB/c mice were used in this study. The tumor was implanted under the breast skin of mice. Mice were divided into five groups, namely control, sham, drug (IV injected of 2 mg/kg of DOX), drug (IV injected of 1 mg/kg of DOX) + US (150 kHz for 15 minutes) and exposure to ultrasound (150 kHz for 15 minutes) alone. The data were analyzed employing ANOVA using SPSS software V.13 and complementary test of Tooki was done. Results: It was shown that, after injection of DOX, exposure to ultrasound at 150 kHz the necrotic spaces in adenocarcinoma tumors compared to control and sham groups have meaningful variance (p<0.001). There was also a significant difference (the bigger the necrotic spaces) between the drug+US group and drug treated group (p<0.05), It should be mentioned that the dose of DOX in drug+US group was reduced to 1mg/kg. Conclusions: The co-administration of DOX and low-intensity ultrasound provided a more effective treatment than the drug alone in murine adenocarcinoma breast cancer. The combined treatment appeared to produce synergistic effects that could prove potentially useful in reducing the side effects of DOX by lowering the required effective dose of the drug while increasing the efficiency of the therapy as a whole.