© 2022, Sociedade Brasileira de Cirurgia Cardiovascular. All rights reserved.Introduction: In this study, we aimed to investigate the relationship between postoperative mortality, morbidity, hospital stay and development of postoperative complications with the glycosylated hemoglobin (HbA1c) level and low left ventricular ejection fraction (LVEF) in diabetic and non-diabetic patients who underwent elective coronary artery bypass (CABG) surgery. Methods: The medical records of patients who underwent CABG at our clinic between January 2015 and December 2019 were retrospectively analyzed. All patients were divided into two groups according to their diabetes mellitus (DM) diagnosis. Diabetic patients were also divided into two groups according to their HbA1c levels. The HbA1c threshold value was 7%. All patients were divided into two groups in terms of LVEF. The LVEF threshold value was 40%. Results: We analyzed 393 patients, of which 304 (77.4%) were male and 177 (45.04%) patients were diabetic. For lower LVEF and HbA1c values, we found no relationship between postoperative mortality, prolonged intensive care unit (ICU) stay and development of postoperative complications. Deep surgical site infection (DSSI) was found to be more common in diabetic patients who had a higher HbA1c value. Length of hospital stay was longer in diabetic patients with HbA1c levels <7%. Conclusion: No statistically significant relationship was found between LVEF and HbA1c levels and postoperative mortality, prolonged ICU stay and postoperative complications.