This study aimed to determine the effect of brazilin on the invasion and metastasis of breast cancer. The breast cancer MDA-MB-231 and 4T1 cells were treated with brazilin to investigate proliferation and invasion using cell proliferation assay, wound healing assay, transwell assay. BALB/C mice were randomized into normal, model, positive control, and Sappan L. extract groups (n=6/group). The mice were injected with 4T1 cells via caudal veins to establish a lung metastasis model and via subcutaneous injection to establish a xenograft model. Metastatic nodules on the lung surface, survival rates and visceral indices were evaluated. Subcutaneous tumor volumes and weights were measured. Brazilin inhibited the proliferation of breast cancer cells and significantly inhibited the wound healing, migration, and invasion of MDA-MB-231 and 4T1 cells. Compared with the normal group, the average survival days and spleen index in the model group were significantly decreased, but the lung index and number of pulmonary metastatic nodules were significantly increased. Compared with the model group, the average survival and spleen index of dose groups were significantly increased, and the lung index, the number of pulmonary metastatic nodules, and tumor volume and weight were significantly decreased. Brazilin significantly inhibits the proliferation and metastasis of breast cancer. This study might suggest a new therapeutic agent for breast cancer.