Introduction & Objective: Hyperglycemia, which occurs during cardiac surgery, has been shown to be associated with increased morbidity and mortality. The management of hyperglycemia during coronary artery bypass graft surgery has been the focus of investigation in recent years. The aim of this study was to evaluate the rate of changes in blood sugar in patients undergoing coronary artery bypass graft surgery and related factors in Dr. Heshmat Hospital affiliated to Guilan University of Medical Sciences as a referral, educational, treatment center and the only subspecialty heart center in Guilan province. Materials & Methods: This descriptive-cross sectional study was done during 2019-2020. Eligible patients’ candidate for elective CABG surgery enrolled the survey. A questionnaire was filled out containing demographic data and blood sugar at 5 measurement point times. Finally, the collected data were entered into SPSS version 21 and after examining the normality of the data, independent t test was used to compare and determine the factors associated with changes in blood sugar in patients undergoing coronary artery bypass grafting from correlation and Chi square tests. Also, to compare the mean changes in blood sugar in patients undergoing coronary artery bypass graft surgery at the times before induction of anesthesia, before the start of the pump, in the middle of the pump, after the pump and at the end of the operation, repeated measure test was used. Results: The data from 55 CABG cases were analyzed. Trend of changes was increasing and significant from baseline to the end of surgery (P ˂0.0001). ASA class III, BMI > 30, age above 60, the history of DM more than 10 years and insulin administration during surgery were significantly associated with higher levels of blood sugar in 5 measurements point times (P ˂ 0.05). Conclusions: We found that blood sugar is well controlled in CABG surgery in Heshmat hospital. But special attention should be paid to ASA class III, BMI > 30, Age above 60, insulin administration during surgery, surgery duration more than 180 minutes and the history of DM more than 10 years.