Aneurysm of the left atrial appendage (LAA) is very infrequent. We present the case of 24-year-old man in functional class I with atrial fibrillation but no other symptoms. Radiology showed an abnormality in the outline of the heart. Echocardiography revealed left appendage aneurysm. After median sternotomy, aneurysmectomy was performed under cardiopulmonary bypass without cross clamping. Atrial fibrillation ceased as soon as the aneurysm had been removed. There were no postoperative complications. Three months later the patient remained asymptomatic and in sinus rhythm.