AbstractIndirubin is widely used as the active component of “Dangui Luhui Wan” in ancient China. However, its effects against the osteosarcoma (OS), the most common primary malignancy, are still unknown. In our present study, we investigated the effects of the Indirubin‐3′‐monoxime (I3M), a derivative of indirubin with better water solubility, against the OS cells. We found I3M inhibited OS cell proliferation in a dose‐dependent manner. Flow cytometry assays showed that I3M could not only induce OS cell apoptosis in a time‐ and dose‐dependent manner but also regulate the cell cycle distribution. Additionally, we demonstrated that several Bcl‐2 family members, cyclin‐dependent kinases (CDKs) and cyclins contributed to this process. Furthermore, out data verified that I3M suppressed OS cell migration and invasion by decreasing MMP‐2 and MMP‐9 levels. Moreover, survivin and focal adhesion kinase (FAK) might play important roles in the anti‐OS effects of I3M. The administration of I3M also inhibited the OS cell growth in mice. Taken together, our results indicated the inhibitory effects of I3M against human OS and thus might be an efficient candidate for OS chemotherapy.