β‐catenin in its role as a nuclear signaling molecule has been implicated in prostate carcinogenesis primarily through modulation of androgen receptor activity. We defined the pattern of β‐catenin protein expression in the nuclei of normal, hyperplastic and malignant human prostate tissue and determined whether differences in expression were associated with disease progression and prognosis. Five normal prostates, 26 benign prostatic hypertrophy specimens, 232 radical prostatectomy specimens from patients with clinically localized prostate cancer (PC) and 20 cases of advanced PC were assessed for β‐catenin expression using immunohistochemistry. Nuclear β‐catenin expression in localized PC was significantly lower than that in benign prostate tissue (p < 0.001) and significantly higher than that in advanced PC tissue (p < 0.001). In addition, lower levels of nuclear β‐catenin expression (< 10% of cancer cells) predicted for a shorter biochemical relapse‐free survival in patients with localized PC (p = 0.008) and were inversely correlated with preoperative prostate‐specific antigen (PSA) levels (p = 0.01). Analysis of the low‐risk subgroup of patients with preoperative PSA levels < 10 ng/ml demonstrated that lower levels of nuclear β‐catenin expression (< 10% of cancer cells) again predicted for a poorer prognosis (p = 0.006). In conclusion, lower levels of nuclear β‐catenin expression are found in malignant compared to benign prostate tissue. In addition, lower nuclear β‐catenin expression is associated with a poorer prognosis in localized PC, in particular, in the low‐risk subgroup of patients with preoperative PSA levels < 10 ng/ml. Thus, the level of nuclear β‐catenin expression may be of clinical utility as a preoperative prognostic marker in low‐risk localized PC.