The impact of diabetes on perioperative outcomes remains incompletely understood. Our purpose is to evaluate post-operative complications and mortality in patients with diabetes. Using the institutional and clinical databases of three university hospitals from 2009⁻2015, we conducted a matched study of 16,539 diabetes patients, aged >20 years, who underwent major surgery. Using a propensity score matching procedure, 16,539 surgical patients without diabetes who underwent surgery were also selected. Logistic regressions were used to calculate the odds ratios (ORs) with 95% confidence intervals (CIs) for post-operative complications and in-hospital mortality associated with diabetes. Patients with diabetes had a higher risk of postoperative septicemia (OR 1.33, 95% CI 1.01⁻1.74), necrotizing fasciitis (OR 3.98, 95% CI 1.12⁻14.2), cellulitis (OR 2.10, 95% CI 1.46⁻3.03), acute pyelonephritis (OR 1.86, 95% CI 1.01⁻3.41), infectious arthritis (OR 3.89, 95% CI 1.19⁻12.7), and in-hospital mortality (OR 1.51, 95% CI 1.07⁻2.13) compared to people without diabetes. Previous admission for diabetes (OR 2.33, 95% CI 1.85⁻2.93), HbA1c >8% (OR 1.96, 95% CI 1.64⁻2.33) and fasting glucose >180 mg/dL (OR 1.90, 95% CI 1.68⁻2.16) were predictors for post-operative adverse events. Diabetes patients who underwent surgery had higher risks of infectious complications and in-hospital mortality compared with patients without diabetes who underwent similar major surgeries.