© 2017 All right reserved by the Turkish Society of Cardiovascular Surgery.Background: This study aims to evaluate the role of SYNTAX and clinical SYNTAX scores in predicting postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting. Methods: I n t his p rospective, s ingle-center, o bservational s tudy, 123 patients (92 males, 31 females; mean age 60 years; range 40 to 84 years) who underwent coronary artery bypass grafting in our hospital between September 2015 and July 2016 were included. Preoperative demographic and clinical characteristics were recorded and SYNTAX and clinical SYNTAX scores were calculated. Univariate and multivariate logistic regression analyses with correlation analysis were used to identify the predictors of postoperative atrial fibrillation. Results: Postoperative atrial fibrillation developed in 39 patients (31.7%). The second day of surgery was the peak time of the complication. SYNTAX [18(9-32) vs 24(10-45), p=0.001] and clinical SYNTAX scores [18(7-44) vs 30(11-89), p < 0.001] were statistically significantly higher in patients who developed postoperative atrial fibrillation. In the correlation analysis, age, SYNTAX, clinical SYNTAX scores, CHADSVASc scores, hemoglobin A1c, and C-reactive protein values were positively associated with the frequency of postoperative atrial fibrillation, while hemoglobin showed a negative correlation (p < 0.05). Clinical SYNTAX scores [(β=0.077, p=0.003, OR=1.080, 95% CI (confidence interval) (1.026-1.137)], SYNTAX [(b=0.081, p=0.028, OR=1.084, 95% CI (1.009-1.165)], and age [(b=0.054, p=0.034, OR=1.056, 95% CI (1.004-1.110)] were found to be independent predictors of postoperative atrial fibrillation in multivariate logistic regression analysis. The receiver operating characteristic analysis showed an area under the curve of 0.68 and 0.75 for SYNTAX and clinical SYNTAX scores, respectively (p=0.01, p < 0.001, respectively). Clinical SYNTAX scores > 17.59 had 84.6% sensitivity and 54.8% specificity to predict postoperative atrial fibrillation (area under curve: 0.754, p < 0.001, 95% CI (0.658-0.850). Conclusion: This study showed that age, SYNTAX, and clinical SYNTAX scores were independent predictors of postoperative atrial fibrillation. Clinical SYNTAX scores may be better than the SYNTAX scores in predicting postoperative atrial fibrillation in patients undergoing coronary artery bypass grafting.