This study was conducted to prospectively assess if there are any outcome differences between patients undergoing coronary artery bypass graft surgery with and without diabetes. This is an 11-year, prospective, hospitalization cohort study. Data were collected on 225 variables. A total of 8935 patients were available for our analysis (6023 nondiabetics, 319 diet-controlled diabetics, 1636 diabetics on oral medications, 957 insulin-controlled diabetics). Compared with nondiabetics, diet-treated diabetics possessed four significant comorbidities, diabetics treated with oral medications possessed 12 significant comorbidities, and insulin-treated diabetics possessed 13 significant comorbidities (P < 0.05). There was no significant difference between diet-treated diabetics and nondiabetics for all outcomes. Diabetics treated with oral medications possessed a longer length of stay [relative risk (RR), 1.09; CI, 1.08-1.10], longer intensive care unit length of stay (RR, 1.56; CI, 1.12-2.00), and more intraoperative complications (RR, 1.42; CI, 1.12-1.66). Insulin-treated diabetics possessed more neurological complications (RR, 2.39; CI, 1.52-3.77), wound complications (RR, 2.42; CI, 1.19-4.95), and renal complications (RR, 2.43; CI, 1.70-3.49), longer length of stay (RR, 1.20; CI, 1.14-1.27), and longer intensive care unit length of stay (RR, 1.33; CI, 1.16-1.48). In diabetics undergoing coronary artery bypass graft surgery, as their diabetes progresses from diet treated with oral medications to insulin-dependent, this is associated with more comorbidities at surgical presentation and more morbidity after surgery.