Androgen-dependent prostate cancer inevitably progresses to incurable castration-resistant prostate cancer (CRPC) after androgen deprivation therapy. Because castration-induced hypoxia-inducible factor (HIF)-1α enhances the transcriptional activity of androgen receptor (AR) at low androgen levels mimicking the castration-resistant stage, HIF-1α is expected to be a promising target for suppression of growth of CRPC. We investigated the effect of resveratrol (3,4′,5-trihydroxy-trans-stilbene) on the growth of human prostate cancer LNCaP xenografts in castrated male BALB/cSlc-nu/nu mice (5 wk old). The mice were administered a control diet or a resveratrol diet (4 g/kg diet) for 40 d. The resveratrol diet significantly suppressed tumor growth compared to the control diet. In LNCaP xenografts, dietary resveratrol decreased the protein level of HIF-1α, but not the AR coactivator β-catenin, and reduced the mRNA levels of androgen-responsive genes. In the control group, β-catenin was predominantly localized in the nucleus with HIF-1α in LNCaP xenografts, whereas dietary resveratrol inhibited the nuclear accumulation of β-catenin. In hypoxic LNCaP cells at a low androgen level mimicking the castration-resistant stage, hypoxia-induced nuclear accumulation of β-catenin was inhibited by resveratrol. Furthermore, resveratrol repressed the expression level of HIF-1α even in the presence of a proteasome inhibitor and suppressed hypoxia-enhanced AR transactivation. These results indicate that dietary resveratrol represses nuclear localization of β-catenin by decreasing the HIF-1α expression, perhaps in a proteasome-independent manner, and inhibits β-catenin-mediated AR signaling; this contributes to suppression of tumor growth of CRPC.