Several studies have shown that postoperative atrial fibrillation (POAF) is associated with poorer short-term and long-term outcomes after general cardiac operations. There is, however, a paucity of data on the impact of POAF on outcomes after isolated aortic valve replacement (AVR). Methods. Data for all patients undergoing isolated first-time AVR between June 2001 and December 2009 was obtained from the Australasian Society of Cardiac and Thoracic Surgeons (ASCTS) National Cardiac Surgery Database Program and a retrospective analysis was conducted. Preoperative characteristics, early postoperative outcome, and late survival were compared between patients in whom POAF developed and those in whom it did not. Propensity score matching was performed to correct for differences between the 2 groups. Results. Excluding patients with preoperative arrhythmia, isolated first-time AVR was performed in 2,065 patients. POAF developed in 725 (35.1 ) of them. Patients with POAF were significantly older (mean age, 72 versus 65 years; p <0.001) and presented more often with comorbidities, including hypertension, respiratory disease, and hypercholesterolemia (all p <0.05). From the initial study population, 592 propensity-matched patient pairs were derived; the overall matching rate was 81.7 . In the matched groups, 30-day mortality was not significantly different between the POAF and non-POAF groups (1.5 versus 1 ; p 0.48). Patients with POAF were, however, at an independently increased risk of perioperative complications, including new renal failure, gastrointestinal complications, and 30-day readmission (p <0.05). Seven-year mortality was not significantly different between POAF and non-POAF groups (78 versus 83 ; p 0.63). Conclusions. POAF is a risk factor for short-term morbidity but is not associated with a higher rate of early or late mortality after isolated AVR.