Saccular coronary artery aneurysm, associated with coronary artery fistula, is a very rare condition. A 48-year-old woman was referred to our hospital for the evaluation of an abnormal shadow on the left cardiac border from a chest X-ray film during regular medical health examination. A huge saccular aneurysm with organized thrombi in the proximal left anterior descending artery (LAD) and coronary artery fistulae from LAD and conus branch of the right coronary artery to pulmonary artery was diagnosed by transthoracic echocardiography, multi-detector computer tomography (MDCT), and coronary angiography. The patient received surgical treatment, including thrombectomy of aneurysm, ligation of the inlet and outlet of aneurysmal sac, coronary artery bypass graft (left internal mammary artery-to-distal LAD), and ligation of fistulae. The postoperative course was uneventful, and postoperative echocardiography and MDCT revealed patent bypass graft; however, a small fistula from proximal LAD across aneurysmal sac to pulmonary artery was observed.