The relationship between diabetes and pancreatic cancer is well documented; however, the effect of preoperative blood glucose levels on prognosis and postoperative complications is currently unclear. The present study aimed to investigate the effect of preoperative blood glucose levels on overall survival (OS) and postoperative complications in patients with pancreatic cancer. This retrospective study included 225 patients with pancreatic cancer treated at The Fourth Hospital of Hebei Medical University from January 2015 to December 2020. Patients were grouped based on preoperative blood glucose levels (normal, <= 6.11 mmol/l; high, >6.11 mmol/l). Data on demographics, clinical history, tumor characteristics, treatment and laboratory results were collected. High preoperative blood glucose levels were associated with reduced OS time [hazard ratio (HR), 1.68; 95% confidence interval (CI), 1.15-2.45; P=0.007] and increased postoperative complications (29.2 vs. 9.8%; chi(2)=13.658; P<0.001). Median OS time was significantly shorter in the high glucose group (14.2 vs. 20.5 months; HR, 1.96; 95% CI, 1.38-2.77; P<0.001). Elevated CA19-9 levels were also a predictor of poor OS (HR, 1.70; 95% CI, 1.06-2.74; P=0.029). High preoperative blood glucose and elevated CA19-9 levels were independent predictors of poor prognosis in patients with pancreatic cancer. This finding suggests that preoperative blood glucose levels have a greater impact on prognosis compared with a history of diabetes. Elevated preoperative blood glucose levels have poorer OS and a higher incidence of postoperative complications compared to those with lower preoperative glucose levels, underscoring the importance of preoperative glucose management. Effective preoperative blood glucose control may improve outcomes in patients with pancreatic cancer.