The possible roles of STEAP4 in cancer progression have not been reported. In this study, we report that STEAP4 expression is able to inhibit anchorage-independent cell growth. We also demonstrate that STEAP4 associates with focal adhesion kinase (FAK) and regulate the activity of FAK through Y397 phosphorylation. Furthermore, we show that CpG sequences in STEAP4 promoter region were frequently methylated in DU145, androgen-independent prostate cancer cells. Demethylation treatment induced STEAP4 expression in DU145, suggesting the possibility that STEAP4 expression in cancer cells is in part epigenetically regulated. Collectively, these data demonstrate a novel function of STEAP4 and that STEAP4 may play an important role in tumor malignancy.