BACKGROUND The advancing age and generally increasing risk profile of patients receiving isolated coronary artery bypass graft (CABG) surgery is expected to raise incidence of new-onset postoperative atrial fibrillation (AFIB) resulting in potentially higher risk of adverse outcomes. In the early postoperative course, new-onset post-CABG AFIB is considered relatively easy to treat and is believed to have little impact on patients' long-term outcome. However, little has been done to determine the effect of new-onset post-CABG AFIB on long-term survival, and this relationship is unclear. RESULTS Survival was assessed in a cohort of 6899 consecutive patients without preoperative AFIB who underwent isolated CABG at Baylor University Medical Center, Dallas, Tex, between January 1, 1997 and December 31, 2006; patients who died during CABG were excluded. Ten-year unadjusted survival was 52.3% (48.4%, 56.0%) for patients with new-onset postoperative AFIB and 69.4% (67.3%, 71.4%) for patients without it. A propensity-adjusted model controlling for risk factors identified by the Society of Thoracic Surgeons and other clinical/nonclinical details was used to investigate the association between new-onset AFIB post-CABG and long-term survival. After adjustment, new-onset AFIB post-CABG was significantly associated (hazard ratio, 1.29; 95% CI, 1.16, 1.45) with increased risk of death. CONCLUSIONS This study provides evidence that new-onset post-CABG AFIB is significantly associated with increased long-term risk of mortality independent of patient preoperative severity. After controlling for a comprehensive array of risk factors associated with post-CABG adverse outcomes, risk of long-term mortality in patients that developed new-onset post-CABG AFIB was 29% higher than in patients without it.