The authors report on a 70-year-old woman with chronic atrial fibrillation that was hospitalized for digitalis intoxication and incidentally was found to have an interatrial lipoma. The diagnosis was established by transesophageal echocardiography, computed tomography (CT) scanning, and magnetic resonance imaging (MRI). Owing to the asymptomatic character and the benign nature of the tumor, a decision for conservative management was made.