Introduction: Although postoperative atrial fibrillation (AF) is one of the most frequent complications of coronary artery bypass graft (CABG) surgery, the utility of echocardiography in the prediction of postoperative AF has been not clear. We investigated the correlation between preoperative left atrial (LA) function used by two dimensional (2D) speckle tracking strain echocardiography and postoperative AF after CABG. Methods: Fifty three patients (mean age 66 짹 9 years) undergoing elective isolated CABG were enrolled in this study. Routine transthoracic echocardiography (TTE) and 2D speckle tracking strain analysis were performed before the surgery. Postoperative AF was detected with continuous electrocardiography(EKG) monitoring throughout hospitalization (mean duration 17 짹 10 days) . Results: Postoperative AF occurred in thirteen of fifty three patients (24%). Patients with postoperative AF were significantly older than patients without postoperative AF (68 짹 8 vs. 62 짹 10 years, p<0.001). Compared with patients without postoperative AF, patients with postoperative AF had a significantly lower value of LA global strain (25.4 짹 7.6 vs. 36.8 짹 10.4 %, p=0.001), and a longer mitral E-wave deceleration time (DT) (249.7 짹 46.4 vs. 214.5 짹 43.7 ms, p=0.016). By multivariate logistic regression analysis, only LA global strain (OR 0.88, 95% CI 0.79 - 0.98, p=0.024) was independent predictor of postoperative AF. Conclusions: Preoperative LA global strain measured by 2D speckle tracking strain analysis could predict the development of postoperative AF after CABG. In other words, preoperative LA function assessed by 2D speckle tracking imaging was significantly related to postoperative AF after CABG.