Tanshinone IIA (TanIIA) is a traditional Chinese agent and has been widely used for treatment of cardiovascular diseases. Our previous study has shown that TanIIA can induce the differentiation of acute promyelocytic leukemia (APL) cells by increasing C/EBPβ expression and induce APL cell apoptosis in vitro. In this study, we evaluated the activity of TanIIA against APL in vivo. We found that treatment with TanIIA prevented APL-mediated reduction in body weights. Treatment with TanIIA inhibited the proliferation of APL cells and triggered APL cell apoptosis and differentiation in vivo. Treatment with TanIIA significantly prolonged the survival of APL-bearing mice. Our data indicate that TanIIA has potent anti-APL activity with little adverse effect.