The outcome is variable for unresectable locally advanced non-small-cell lung cancer (ULANSCLC) patients treated with radio(chemo)therapy. The aim of this study is to investigate whether single-nucleotide polymorphisms (SNPs) in the transforming growth factor-beta1 (TGF-β1) gene are associated with overall survival (OS) in ULANSCLC patients treated with definitive radio(chemo)therapy. A total of 109 patients who had available blood samples and complete clinical and follow-up information were enrolled. DNA from blood was genotyped for two SNPs: TGF-β1 C-509T and T+869C. Kaplan-Meier survival analysis, log-rank test, and Cox's proportional hazard model were used to evaluate associations between genotypes and OS. Log-rank test showed that TGF-β1 C-509T significantly correlated with OS (pooled P = 0.017). Both univariate and multivariate analyses showed that TGF-β1 C-509T CC genotype was significantly associated with better OS than CT or TT genotypes. These results indicate that TGF-β1 C-509T CC genotype is significantly associated with better OS in ULANSCLC patients treated with radio(chemo)therapy as a potential independent survival predictor.