Study Design. Xenograft osteosarcoma mouse model. Objective. We determined the effect of lycorine on osteosarcoma. Summary of Background Data. Osteosarcoma is an aggressive malignant neoplasm, is most prevalent in teenagers and adults and current treatment approaches have reached a survival plateau and attempts to improve osteosarcoma prognosis have proven unsuccessful. Thus there is clear evidence that development of new agents with high efficacy and fewer side effects to provide better prognostic outcome is urgently needed. Methods. The toxicity, function and mechanism of lycorine (LY) on osteosarcoma were accessedin vitroby CCK-8 assay, flow cytometry, and western blotting andin vivoby the xenograft osteosarcoma mouse model. Results. In this study, we found that LY exhibited dose-dependent and time-dependent cytotoxic effects on human osteosarcoma cell-lines SJSA-1 and U2OS, inducing G1 phase cell cycle arrest and cellular death via apoptosis. Mechanistically, LY treatment elevated ROS generation that activates the p38 mitogen-activated protein kinases (MAPKs) and p53-dependent apoptotic program. Inhibition of ROS generation by NAC or p38 MAPK signaling by SB203580 attenuated the p53-mediated cell cycle arrest and apoptosis induced by LY.In vivoadministration of LY markedly reduced tumor growth with little organ-related toxicity in a mouse xenograft model of osteosarcoma. Conclusion. Collectively, our data suggests that LY exhibit therapeutic potential for the treatment of osteosarcoma.