Abstract Background: Atrial fibrillation (AF) is the most common cardiac arrhythmia following coronary artery bypass grafting (CABG). We hypothesized that measures of left atrial (LA) function would be useful in predicting AF in patients undergoing CABG. Methods and Results In the study, 611 patients were included after CABG. All patients had echocardiograms performed preoperatively and LA functional measurements were assessed. These measurements were LA maximum volume index (LAVmax), LA minimum volume index (LAVmin) and LA emptying fraction (LAEF). The endpoint was AF occurring >14 days after surgery. During the follow-up period of a median of 3.7 years, 52 (9%) developed AF. The mean age was 67 years, 84% were male and the average left ventricle ejection fraction was 50 %. No differences were observed between the patients developing AF and those who did not develop AF. No functional LA measurements were significant predictors of AF in the whole CABG population. However, in patients with normal-sized LA (n=532, events: 49), both LAEF and LAVmin were univariable predictors of AF. When the functional measurements were adjusted for the CHADS ₂ score, both LAVmin (HR=1.07 (1.01-1.13), p=0.014 ) and LAEF (HR: 1.02 (1.00-1.03, p= 0.023)), remained significant predictors. Conclusion No echocardiographic measurements were significant predictors of AF after CABG. In patients with a normal LA size, LAVmin as well as LAEF were significant predictors of AF. Keywords: atrial fibrillation; cardiac surgery; left atrium; echocardiography