Background: The aim of this study was to clarify the oncological safety of pylorus-preserving gastrectomy (PPG) compared with conventional distal gastrectomy (DG). Methods: From three institutions specializing in cancer, the medical records for a cohort of 2,898 consecutive patients who had undergone DG (n = 2,208) or PPG (n = 690) for clinical Stage I gastric cancer between January 2006 and December 2012 were analyzed. A propensity score for each patient was estimated based on 38 preoperative clinical and tumor related factors. After propensity score matching, 1,004 patients (DG = 502, PG = 502) were included in the analysis. The overall survival, relapse free survival and occurrence of secondary gastric cancer were then compared. The median (range) observation period was 48.6 (1-109.8) months. Results: The patients who received a PPG were relatively young age (58.7 ± 10.4 years) and had a high performance status, middle gastric tumor, solitary tumor, clinical T1, and clinical N0. The 5-year overall survival was 98.4 % for the PPG group and 96.6% for the DG group (Hazard ratio: 0.48, 95%CI: 0.21 - 1.09, P= 0.07). The 3-year relapse-free survival was 99.5% for the PPG group and 98.0% for the DG group (HR: 0.39, 95%CI: 0.12 – 1.33, P= 0.12). Postoperative secondary gastric cancer was encountered in 8 (1.6 %) in the PPG group and 4 patients (0.8 %) in the DG group. No significant differences in either overall survival, relapse free survival or the occurrence of secondary gastric cancer were observed between the two groups. Conclusions: Given the adequate estimation of the clinical tumor stage, the oncological safety of PPG for clinical T1N0 gastric cancer in the middle stomach was comparable to that of DG.