OBJECTIVE: The minimised extracorporeal circulation (MiECC) system is an alternative to the classical extracorporeal circulation (ECC) system in coronary artery bypass grafting (CABG) surgery. Some publications reported that there are few studies on the relationship between this application and the development of postoperative atrial fibrillation (POAF) and that differences in results were observed. We aimed to evaluate the possible relationship between the use of MiECC and the development of early atrial fibrillation (AF) in isolated on-pump CABG patients. METHODS: This study was conducted in patients who underwent isolated on-pump CABG surgery. Patients with known preoperative AF were not included in the study. Patients were examined in Group 1: classical ECC group and Group 2: MiECC group. RESULTS: The mean age of a total of 38 patients included in the study was found to be 62,03 ± 9,58. The AF development was found to be 0,13 ± 0,34. Group 1 and Group 2 groups did not differ with respect to aortic cross-clamp time, cardiopulmonary bypass (CPB) duration, and the number of distal anastomoses (p value was 0,809, 0,473, and 0,116, respectively). No statistically significant difference was found between the two groups in terms of postoperative AF development (p = 0.337). CONCLUSION: According to our evaluation based on the results of our study, we conclude that MiECC usage in isolated on-pump CABG does not independently reduce the incidence of postoperative AF. Since existing literature presents divergent findings, we believe that studies focusing on the development of POAF and including more patients would be useful.