Transforming growth factor β1 (TGF-β1) is a cytokine that plays an important role in the control of cell proliferation and differentiation in breast cancer. The -509C/T polymorphism in the TGF-β1 gene has been implicated in breast cancer risk. However, studies on the association between this polymorphism and breast cancer risk have produced conflicting results. To derive a more precise estimation of the relationship, a meta-analysis of the -509C/T polymorphism (5,825 cases and 7,953 controls) from seven published case-control studies was performed. Our analysis suggests that -509C/T has no association with breast cancer risk when using either dominant [odds ratio (OR) = 1.01, 95% confidence intervals (CI): 0.82-1.24], or recessive models (OR = 0.91, 95% CI: 0.66-1.27), or other genetic models to analyze the data. In ethnic subgroups analysis, -509C/T also did not appear to be a risk factor for breast cancer. However, larger scale primary studies are still required to further evaluate the interaction of TGF-β1 -509C/T polymorphism and breast cancer risk in specific populations.