Transglutaminase 4 has been shown to enhance various biological properties of prostate cancer cells, e.g., cell-matrix adhesion, invasiveness and the epithelial-mesenchymal transition. The objectives of this study were to investigate the associations between transglutaminase 4 expression and the established features and biochemical recurrence of prostate cancer. Transglutaminase 4 immunostaining was performed on a tissue microarray. The expression of transglutaminase 4 was evaluated by a scoring method based on the intensity and extent of staining. The clinical and pathological information was obtained through a review of medical records. Follow-up data were obtained by consulting the hospital medical records and the prostate cancer database of our department and by contacting patients or family members. We then compared the transglutaminase 4 expression levels between the prostate cancer tissues and the paracarcinoma tissues and evaluated the correlation of transglutaminase 4 expression with the clinical parameters and biochemical recurrence of prostate cancer. Our results indicated that the transglutaminase 4 staining was significantly higher in tumour tissue than in paracarcinoma tissue (P<0.001) and was positively associated with higher Gleason score (P<0.001) and higher prostate-specific antigen level (P=0.005). Patients with transglutaminase 4 overexpression experienced shorter biochemical recurrence-free survival after surgery (P=0.042) in the univariate analysis but not in the multivariate analysis (P=0.139), which indicated that transglutaminase 4 may serve as a potential predictor of biochemical recurrence of prostate cancer.