The association between COMT Val158Met polymorphism and prostate cancer has been evaluated. However, the results of these studies on the association remain conflicting. To derive a more precise estimation of the relationship, a meta-analysis was performed. A comprehensive search was conducted to identify the eligible studies of COMT Val158Met polymorphism and prostate cancer risk. Summary odds ratios (OR) and 95 % confidence interval (CI) for COMT Val158Met polymorphism and prostate cancer were calculated. Statistical analysis was performed with the software program Review Manage (Version 5.0) and Stata (Version 12.0). Six case-control studies, totally 4,118 persons including 2,143 cases and 1,975 controls, met the included criteria and thus were selected. Our analysis suggested that Val158Met polymorphism was associated with prostate cancer risk in overall population. Collectively, the results of the present study suggest that significant associations of COMT Val158Met polymorphisms with prostate cancer were observed (for additive model: OR = 1.068, 95 % CI = 1.002-1.138, P (heterogeneity) = 0.363, P = 0.043; for dominant model: OR = 1.266, 95 % CI = 1.057-1.517, P (heterogeneity) = 0.000, P = 0.011; for recessive model: OR = 1.050, 95 % CI = 0.961-1.146, P (heterogeneity) = 0.558, P = 0.279; and Val allele versus Met allele OR = 0.932, 95 % CI = 0.894-0.971, P (heterogeneity) = 0.272, P = 0.001). In the subgroup analysis, we detected no significant association between the COMT 158 Val/Met genotype and prostate cancer risk in Caucasian and Asian populations, while the contrary result for additive model (OR = 2.43, 95 % CI = 1.08-5.43, P (heterogeneity) = 0.04, P = 0.03) in Asian populations. The result of this meta-analysis suggests that COMT l58Val/Met polymorphism might be contributed to the overall prostate cancer risk.