Background: No data are present currently on the potential correlation between postoperative hyperglycemia and long-term outcomes after gastric surgery for cancer. The aim of this study was to investigate the effects of postoperative hyperglycemia on survival after curative gastrectomy for cancer. Methods: All patients who underwent gastric surgery for cancer with curative intent were reviewed retrospectively. Diabetic patients and patients who needed pancreatic resection were excluded. In all patients, a prepared intravenous infusion of NaCl and carbohydrates (Isolyte Baxter 2,000 mL/day; glucose 50.0 g/L;Ringers lactate 1,000 mL/day) was used, and the patients were kept nil by mouth until the fourth postoperative day. The glucose levels were monitored during the first 72 hours. The study population was divided into normoglycemic and hyperglycemic patients according to the blood glucose level (<140 mg/dL and ≥140 mg/dL, respectively). The 2 groups were matched for age, sex, type of operative procedure, TNM status, and lymph node status. Results: After matching, 104 patients were included for the analysis. Perioperative morbidity accounted for 18.3% with a greater rate for hyperglycemic patients (12% vs 31%; P = .018). When compared with normoglycemic patients, hyperglycemic patients had worse overall survival (45% vs 57%; P = .05) and worse disease-free survival (46% vs 68%; P = .02). On the multivariate analysis, hyperglycemia was an independent risk factor for a worse overall and disease-free survival. Conclusion: Postoperative hyperglycemia owing to surgical stress conditions can affect postoperative outcomes. Additionally, hyperglycemia may be a factor that promotes gastric cancer progression.