A right atrial separation procedure was performed for the ablation of atrial fibrillation during the concomitant repair of an atrial septal defect. This procedure consisted of a Y-shaped incision in the right atrium, followed by cryoablation of the tricuspid annulus and the atrial septum without any procedures performed on the left atrium. This is a simple and effective method for the elimination of chronic atrial fibrillation associated with atrial septal defects in adults.