Poor prognosis in ovarian clear cell carcinoma is associated with the expression of a defined set of proteins including osteopontin (OPN) and integrin. Statins, a family of 3-hydroxy-3-methylglutaryl CoA reductase inhibitors, are currently being investigated for the treatment and prevention of cancer. In this study, we investigated the effects of simvastatin on ovarian clear cell carcinoma (OCCC) cells in vitro and in vivo and elucidated the mechanism of drug action. Changes in OPN gene expression were determined by real-time RT-PCR, and an MTT assay was performed to determine effects on cell proliferation. Finally, a xenograft tumor model was constructed to evaluate the effects of simvastatin on cell proliferation and apoptosis in vivo. According to our experimental results, OPN is an important protein in OCCC. Simvastatin inhibited OCCC cell proliferation, and the inhibition rate was approximately 40% to 50% after treatment with 10 µM simvastatin for 48 h. In the xenograft studies, simvastatin treatment resulted in a significant growth inhibition. Furthermore, the mice treated with simvastatin survived significantly longer compared to the control groups. In conclusion, simvastatin has anticancer effects in vitro and in vivo. Further confirmation of the anticancer effects of statins in future studies will increase the scope for OCCC treatment.