Background: Postoperative complications increased recurrence in gastric cancer (GC) patients. However, there was no study evaluating impact of postoperative complication among patients receiving adjuvant chemotherapy. The aim of present study was to investigate the impact of postoperative complications in pStage II/III GC patients who received adjuvant S-1 chemotherapy. Methods: The present study retrospectively examined GC patients who received curative gastrectomy followed by adjuvant S-1 chemotherapy between January 2000 and December 2011 at Kanagawa Cancer Center. The patients with postoperative complications were classified into PC group, and those without postoperative complications were into NC group. Clinicopathological characteristics and recurrence-free survival (RFS) were compared between the groups. Results: 226 patients were included in this study. Postoperative complication occurred in 30 patients (13.3%). Age (Median, range) is significantly higher in NC group (64, 24-86) than in PC group (59, 36-82) (p = 0.033). Total gastrectomy was predominant type of surgery in the PC group (73.3%) than in NC group (52.0%) (p = 0.031). There was no difference in gender, ASA score, tumor location, pathological stage (TNM 7th) and pathological type between two groups. Conclusions: Postoperative complications were an independent risk factor for RFS in pStage II/III GC patients who received curative gastrectomy followed by adjuvant S-1 chemotherapy.