Hyperglycemia occurs commonly in clinically ill patients. Insulin therapy and glycemic control have been recommended for patients with septic shock. The present study investigated the effect of intensive (INIT) versus conventional insulinotherapy (COIT) in cardiac surgery patients who received cardiopulmonary bypass (CPB). In this quasi-experimental study, a total of 50 patients undergoing coronary artery bypass grafting (CABG) were recruited into the INIT and COIT groups. Study measures included serum glucose levels, cardiac output, cytokines, C-reactive protein (CRP), duration of mechanical ventilation and length of stay in the intensive care unit (ICU), and ICU mortality rate. In the INIT group, mean blood glucose level during the first two postoperative days was significantly lower than that in the COIT group. Cardiac output was significantly greater at the second postoperative days in the INIT patients than those in the COIT group. There were no differences in cytokines, CRP levels and the outcome data between two groups. Intensive insulinotherapy reduced the blood glucose and led to improve cardiac output after CABG in comparison with conventional insulinotherapy.