Transforming growth factor-β1 (TGF-β1) is negative regulator of cell proliferation and the cell cycle, and plasma levels of TGF-β1 are twice as high in TGF-β1 -509 T homozygotes as in -509 C homozygotes. Published studies on the association between the TGF-β1 gene -509 C/T polymorphism and breast cancer risk are inconclusive, and a meta-analysis is required to verify the association. We performed a meta-analysis of four studies, including a total of 5,986 cases and 6,829 controls. Our pooled results indicate that the TGF-β1 gene -509 C/T polymorphism is not associated with breast cancer risk in a TT versus CC codominant (OR = 1.08; 95% CI = 0.87-1.34; P = 0.494), in a CT versus CC codominant (OR = 1.02; 95% CI = 0.94-1.10; P = 0.686), recessive (OR = 0.92; 95% CI = 0.83-1.03; P = 0.157), and dominant (OR = 1.03; 95% CI = 0.96-1.11; P = 0.439) models. Conclusively, this meta-analysis suggests that the TGF-β1 gene -509 T allele polymorphism does not decrease breast cancer risk.