Xiao Jin Wan (XJW) is a well-known traditional Chinese folk-medicine, which is commonly used for the treatment of various types of diseases including cancers. However, the mechanism of the anticancer activity of XJW against U-2OS human osteosarcoma cells, have not yet been reported. In the present study, we investigated the cellular effects of the XJW on the U-2OS human osteosarcoma cell line. Our results showed that XJW induced cell morphological changes, reduced cell viability in a dose- and time-dependent manner and arrested in the G2/M phase of the cell cycle suggesting that XJW inhibited the proliferation of U-2OS cells. Hoechst 33258 staining and Annexin V/propidium iodide double staining exhibited the typical nuclear features of apoptosis and increased the proportion of apoptotic Annexin V-positive cells in a dose-dependent manner, respectively. In addition, XJW treatment caused loss of plasma membrane asymmetry, collapse of mitochondrial membrane potential, activation of caspase-9 and caspase-3, and increase of the ratio of pro-apoptotic Bax to anti-apoptotic Bcl-2. Taken together, the results indicate that the U-2OS cell growth inhibitory activity of XJW was due to cell cycle arrested and mitochondrial-mediated apoptosis, which may partly explain the anticancer activity of Xiao Jin Wan.