Statin, 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor, is known to promote bone formation. However, it is not clear whether statin affects the differentiation of pulp cells. This study used a cell proliferation assay, cell cycle analysis, quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and in vivo transplantation to examine the effects of simvastatin on human dental pulp stem cells (DPSCs) in vitro and in vivo. Simvastatin at 1 mumol/L was able to significantly suppress the proliferation of DPSCs without inducing apoptosis. Quantitative RT-PCR revealed both osteocalcin and dentin sialophosphoprotein to be significantly up-regulated when DPSCs were cultured with simvastatin in comparison to bone morphogenetic protein-2 treatment. The in vivo transplantation data showed that simvastatin treatment promoted mineralized tissue formation. Taken together, these results suggest that statin might be an ideal active ingredient to accelerate the differentiation of DPSCs.