This study compares outcomes of patients with preoperative atrial fibrillation undergoing coronary artery bypass grafting (CABG) with or without concomitant atrial fibrillation ablation in a nationally representative Medicare cohort. This study examined early and late outcomes in CABG patients with a preoperative history of atrial fibrillation to determine the correlation between surgical atrial fibrillation ablation to mortality and stroke or systemic embolization. In the Medicare-linked Society of Thoracic Surgeons database, 361,138 patients underwent isolated CABG from 2006 to 2013; 34,600 (9.6%) had preoperative atrial fibrillation; 10,541 (30.5%) were treated with surgical ablation (ablation group), and 23,059 were not (no ablation group). Propensity score matching was performed using a hierarchical mixed model. Long-term survival was summarized using Kaplan-Meier curves and Cox regression models with robust variance estimation. The stroke or systemic embolization incidence was modeled using the Fine-Gray model. Median follow-up was 4 years. Long-term mortality in propensity score-matched CABG patients (mean age 74 years; Society of Thoracic Surgeons risk score, 2.25) receiving ablation versus no ablation was similar (log-rank P = .30). Stroke or systemic embolization occurred in 2.2% versus 2.1% at 30 days and 9.9% versus 12.0% at 5 years (Gray P = .0091). Landmark analysis from 2 to 5 years showed lower mortality (hazard ratio, 0.89; 95% confidence interval 0.82-0.97; P = .0358) and lower risk of stroke or systemic embolization (hazard ratio, 0.73; 95% confidence interval, 0.61-0.87; P = .0006) in the ablation group. Concomitant ablation in CABG patients with preoperative atrial fibrillation is associated with lower stroke or systemic embolization and mortality in patients who survive more than 2 years. Copyright © 2019 The American Association for Thoracic Surgery. Published by Elsevier Inc. All rights reserved.