Introduction: The role of conformal radiotherapy (cRT) in thoracic esophageal squamous cell carcinoma (TESCC) has not been addressed in adjuvant settings. The aim of this study was to investigate whether postoperative radiotherapy using cRT after an R0 resection improves outcomes in pT3N0M0 TESCC compared with resection alone. Methods: This study included 678 patients with pT3N0M0 TESCC who were treated at the Cancer Hospital, Chinese Academy of Medical Sciences, from January 2004 to December 2011. The patients were divided into two groups: a surgery plus cRT group (S+cRT group) comprising patients who underwent cRT after an R0 resection and a surgery group (S group), comprising a control group of patients who underwent an R0 resection alone. Propensity score matching was used to create patient groups that were balanced across several covariates (n = 83 in each group). Outcome measures included overall survival (OS), disease free survival (DFS), and recurrence. Results: In the overall study cohort, 5-year OS (75.2% versus 58.5%, p = 0.004) and DFS (71.8% versus 49.2%, p = 0.001) rates were significantly higher in the S+cRT group than in the S group. These data were confirmed in the matched samples (5-year OS, 75.7% versus 58.8% [p = 0.017]; DFS, 71.7% versus 50.3% [p = 0.009]). The overall (p = 0.001) and locoregional (p = 0.004) recurrence rates in the S+cRT group were significantly lower than in the S group. Multivariate Cox analyses in the matched samples revealed that surgery and postoperative cRT were independently associated with longer OS (hazard ratio = 0.505, 95% confidence interval: 0.291-0.876, p = 0.015) and longer DFS (hazard ratio = 0.513, 95% confidence interval: 0.309-0.854, p = 0.010) than resection alone. Conclusions: Postoperative radiotherapy using cRT is strongly associated with improved OS and DFS in patients with pT3N0M0 TESCC. A multicenter, randomized phase III clinical trial is warranted to confirm these findings. (C) 2017 International Association for the Study of Lung Cancer. Published by Elsevier Inc. All rights reserved.