['Atrial fibrillation (AF) is the most common arrhythmia following coronary artery by-pass graft surgery (CABG). The value of SYNTAX score to predict postoperative atrial fibrillation (PoAF) has not been clearly addressed. We aimed to evaluate this relationship in patients undergoing isolated CABG.', 'This study was designed as a single-center, non-randomized, observational, prospective study. Ninety-four patients undergoing isolated on-pump CABG, who had sinus rhythm and were older than 18 years, were enrolled. Demographic characteristics of the patients were recorded; SYNTAX score was calculated preoperatively for each patient. The univariate and multivariate logistic regression analysis were used to determine for predictors of PoAF.', 'The median SYNTAX score of the enrolled patients was 21, (56-5). PoAF was observed in 31 (33.3%) patients. Univariate logistic regression showed that age, chronic obstructive pulmonary disease (COPD), red blood cell distribution width (RDW), urea, initial troponin I, peak postoperative troponin I, interventricular septum, left atrial diameter, and SYNTAX score were significantly associated with the frequency of PoAF following CABG. An independent association was identified with age [ß: 0.088, p:0.023, OR: 1.092, 95% CI (1.012-1.179)], COPD [(ß: 2.222, p:0.003, OR: 9.228, 95% CI (2.150-39.602)], and SYNTAX score [(ß: 0.130, p:0.002, OR: 1.139, 95% CI (1.050-1.235)].'] Does sYNTAX score predict postoperative atrial fibrillation in patients undergoing on-pump isolated coronary artery bypass grafting surgery?