The association between the polymorphism of catechol-O-methyltransferase (COMT) Val158Met and breast cancer risk is still inconclusive. We performed a meta-analysis to derive a more precise estimation of the relationship. A total of 18 studies including 5,175 cases and 6,463 controls were involved in this meta-analysis. When all studies were pooled into the meta-analysis, no significantly elevated breast cancer risk was associated with all genetic models (for additive model: OR = 1.273, 95% CI = 0.947-1.711, P heterogeneity = 0.000; P = 0.110; for dominant model: OR = 1.080, 95% CI = 0.945-1.234, P heterogeneity = 0.001; P = 0.259; for recessive model: OR = 1.242, 95% CI = 0.941-1.641, P heterogeneity = 0.000; P = 0.126; for allele comparison model: OR = 1.096, 95% CI = 0.976-1.230, P heterogeneity = 0.000; P = 0.121). In the subgroup analysis by controls source, the same results were found in all genetic models. In summary, this meta-analysis suggests that the COMT Val158Met polymorphism is not a risk factor for breast cancer development. However, large sample and representative population-based studies with homogeneous breast cancer patients and well-matched controls are warranted to confirm this finding.