We describe a rare case of surgical repair of a coronary artery aneurysm with arteriosclerotic changes accompanied by coronary arteriovenous fistula (CAVF) after 26 years of conservative therapy. A 71-year-old woman, diagnosed with CAVF 26 years previously, was admitted to our hospital for general fatigue and dyspnea on exertion. Physical examinations revealed that the CAVF originated from the distal portion of the left circumflex artery (LCX), draining into the coronary sinus (CS); it affected the coronary artery aneurysm with arteriosclerotic changes and was calcified from the left coronary main trunk to the distal portion of the LCX. Treatment without resection of the calcified coronary aneurysm was suggested because of fear of excessive bleeding. The CAVF was closed directly from inside the dilated coronary sinus under cardiopulmonary bypass. The dilated ostium of the left coronary artery was closed using a Xenomedica patch. Coronary artery bypass grafting was performed in the left anterior descending artery (LAD) and posterolateral branch (PL) of the LCX using saphenous vein grafts. Postoperatively, the coronary aneurysm was spontaneously thrombosed for low blood flow. The bleeding might have been uncontrolled if the arteriosclerotic and calcified coronary aneurysm had been incised. Therefore, we successfully thrombosed the calcified coronary aneurysm without resection, after reducing the systemic blood flow to the coronary aneurysm and sustaining the coronary blood flow, performed with CABG.