A 69-year-old man was referred to our hospital with a diagnosis of non-ST elevation myocardial infarction. A selective left coronary angiography revealed a fistula connecting the left main coronary artery with the pulmonary artery in addition to severe left main coronary artery disease. The patient subsequently underwent ligation of fistulae and coronary bypass grafting. The combination of a fistula and severe artery disease seen in this patient is unusual because fistulas originating from the left main coronary artery drain into the pulmonary artery in patients with severe left main coronary artery disease.