Background: Postoperative atrial fibrillation (POAF) is a common and potentially morbid complication following cardiac surgery. It was reported to be associated with greater inhospital mortality; prolonged hospital stays. In addition, the long-term survival was worse in patients who developed POAF. Patients who develop POAF incur additional hospital treatment cost and 2-to-4-fold increased risk of major adverse cardiac events. Objective: To determine the possible predictors of POAF after coronary artery bypass surgery and its impact on outcome. Methods: Two hundred patients were enrolled; they were divided into 2 groups; Group I (n = 100 patients) developed POAF and group II (n = 100 patients) did not developed POAF. All patients were subjected to history, examination, ECG, echocardiography, laboratory investigation as CBC, coagulation profile, kidney function tests, liver enzymes and high sensitivity troponin and coronary angiography to assess severity of coronary artery disease by SYNTAX score. Results: POAF score which contain 9 variables: Age >60 y, Smoking, COPD, CP bypass time (min) >86.5, Vent. Time <23.5, PLR >113.4, LVEF <53.5, RV function by TAPSE <2.15 and Syntax score >34.5. Each variable takes points according to multivariate analysis with total score 20. ROC curve analysis was done to pick up the best cut off value of POAF Score and incidence of POAF which revealed POAF Score more than 10 has sensitivity 99 % and specificity 86% Area under the curve 0.99. Conclusion: POAF after CABG is associated with higher morbidity and mortality, prolonged recumbence in the hospital. Prediction of POAF might be useful in detection of patients at risk for these complications using POAF risk score.