Metastasis is the major cause of death in breast cancer patients. In this study, we investigated the effects of baicalin, a natural compound, on cell migration, invasion and metastasis using human breast cancer MDA-MB-231 cell line as model system. Baicalin not only dose-dependently inhibited MDA-MB-231 cells migration and in vitro invasion, but also suppressed the tumor outgrowth and the pulmonary metastasis of MDA-MB-231 cells in xenograft model. Importantly, treatment of baicalin caused little change in body weight, liver and kidney function of recipient animals. Tumorigenesis-inhibitory effect is likely linked to the capability of baicalin to downregulate metalloproteinase (MMP)-2, MMP-9, urokinase-type plasminogen activator (uPA) and uPA receptor (uPAR) expression in MDA-MB-231 cells. As baicalin blocked p38 mitogen-activated protein kinase (MAPK) activity and treatment of p38MAPK inhibitor SB203580 led to the reduction of MMP-2, MMP-9, uPA and uPAR expressions, we concluded that baicalin suppresses the tumorigenecity of MDA-MB-231 cells by down-regulating MMP-2, MMP-9, uPA and uPAR expressions through the interruption of p38MAPK signaling pathway.