We report the case of a 62-year-old woman who presented with classic symptoms of stable angina. Cardiac images and catheterization results revealed absent pulmonary valve syndrome and compression of the left main coronary artery by a massively dilated pulmonary artery aneurysm. The patient''s anginal symptoms were relieved after pulmonary arterioplasty.Others have described proximal left main coronary artery compression in the presence of a dilated and hypertensive pulmonary artery. To our knowledge, this is the first case in which a pulmonary artery aneurysm caused left main coronary insufficiency in the absence of pulmonary hypertension—a clinically important complication of congenital pulmonary valve-related pulmonary arteriopathy.