Introduction: Postoperative atrial fibrillation (FAPo) is the most common complication after cardiac surgery. We analyzed the incidence of FAPo and we identified the predictors of its occurrence after coronary artery bypass graft ing. Methods: We included in the study 68 patients (54 men and 14 women), after myocardial revascularization by coronary artery by-pass grafting. All patients were fully evaluated clinically and laboratory (biological, electrocardiographic rhythm Holter monitoring, echocardiography) during hospitalization. There were studied pre-, intra- and postoperative predictors involved in the FAPo occurrence. Results: From 68 patients included in the study, 27 had atrial fibrillation (39.7%). We found that from the risk factors incriminated in the development of FAPo, the age over 65 years was present in 51.85% of patients, grade I-II obesity and hypertension in 66.66%. The increased size of the left atrium, an important predictor of FAPo occurrence, was observed in 70.37% of patients, and left ventricular systolic dysfunction in the case of 37.03%. From the intraoperative factors involved in the occurrence of FAPo we proved that: the duration of by-pass heart-lung, the duration of the aortic clamping and the number of by-pass coronary artery grafting sites were predictive in the development of FAPo. Pericarditis and dyselectrolytemias were also more common among patients with FAPo. Conclusions: Atrial fibrillation represents the most common arrhythmia encountered in the early postoperative phase, its incidence being significantly increased compared with other arrhythmias. The presence of atrial fibrillation in patients with coronary artery bypass grafting is associated with the presence of clinical factors, biological and echocardiographic factors (left atrial diameter and left ventricular ejection fraction), suggesting multiple mechanisms of production.