The aim of this study is to evaluate the relationship between Body Mass Index (BMI) and the outcomes of isolated CABG (Coronary Artery Bypass Graft) performed in Shahid Madani Hospital of Khorramabad, Iran. Data was retrospectively collected from the medical records retrieved from the hospital records office. All patients who had undergone isolated CABG under cardiopulmonary bypass in the Cardiothoracic Unit from 2007 till 2013 were identified and their demographic and clinical data were collected. Clinical data included BMI, ejection fraction (EF), history of COPD, MI, CVA, diabetes mellitus, hyperlipidemia, hypertension and the main outcomes included pulmonary complications, renal complications, transfusion, duration of ventilation, reoperation, intensive care unit stay, hospital stay and death. Patients were divided into six groups according to the BMI as follows: group 1: (BMI < 18.5), group 2: (18.5 ≤ BMI < 25), group 3: (25 ≤ BMI < 30), group 4: (30 ≤ BMI < 35), group 5: (35 ≤ BMI < 40), group 6: (BMI ≥ 40). Finally, perioperative variables in the six mentioned groups were compared using appropriate statistical methods. The obtained data were analyzed using SPSS software. In this study, 648 patients met the inclusion criteria of the study. The average age of the patients in the study was reported to be 61.35 ± 10.72 years. The average BMI was reports as 26.3 ± 4.03. The average cardiopulmonary bypass time was compared between the various BMI groups, which showed that the highest average belonged to group V+ (groups V and VI) and the lowest average belonged to group I, but this difference was not statistically significant (PV > 0.05).There was no statistically significant difference between the groups in terms of the mean duration of mechanical ventilation, mean extubation time, drainage rate from the chest tube, and the amount of blood transfusion (PV > 0.05). Moreover, in 99.4% of the patients, broad-spectrum antibiotics, in 99.5% of the patients, inotropic drugs, and in 5.4% of the patients, IABP were used. Re-intubation was done in 3.1% of the patients. The average duration of hospitalization was 5.45 ± 1.48. There was no statistically significant difference between the groups in terms of hospitalization time (PV>0.05). In this study, 3.55% of the patients died. Smirnov and Kolmogorov tests showed that the distribution of quantitative variables is not normal in all the patients (PV<0.001). Therefore, to study the relationship between these quantitative variables, the Spearman correlation coefficient was used, which showed that none of the relationships were statistically significant. Therefore, considering these results, it can be suggested that if there is enough time before surgery, changes in the lifestyle of the individual be recommended so that he/she can attain a better health status. So, proper training and education can be very effective.