Although mounting evidence has demonstrated an important role of Wnt/beta-catenin signaling in the development and progression of cancer, the therapeutic potential of small molecules that target this pathway for prostate cancer remains largely unknown. We reported herein that the highly invasive androgen-independent PC-3 and DU145 human prostate cancer cells exhibited higher levels of Wnt/beta-catenin signaling than the androgen-dependent LNCaP prostate cancer cells and non-cancerous PZ-HPV-7 and PWR-1E prostate cells, and that exogenous Wnt3A treatment exaggerated the difference of the Wnt/beta-catenin signaling levels among these prostate cells. Furthermore, we demonstrated that the non-steroidal anti-inflammatory drug, sulindac sulfide, the cyclooxygenase-2 (COX-2) selective inhibitor, celecoxib, and the nitric oxide-donating aspirin derivative, NO-ASA, blocked Wnt/beta-catenin signaling in PC-3 and DU145 cells. These effects occurred at concentrations comparable to those required to inhibit cell proliferation, indicating that the inhibitory effect of these drugs on prostate cancer cell proliferation may involve the suppression of Wnt/beta-catenin signaling. Finally, we showed that a novel small molecule inhibitor of Wnt/beta-catenin signaling, PKF118- 310, inhibited Wnt/beta-catenin signaling and proliferation in prostate cancer cells within the same concentration range. Together, these results suggest that small molecules that inhibit Wnt/beta-catenin signaling have therapeutic potential for the prevention or treatment of prostate cancer.