Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital cardiac disease with serious complications. This is a case of a three-year-old female who was initially diagnosed and managed as a case of dilated cardiomyopathy. A 2-D echocardiogram showed the left main coronary artery to be coming from the pulmonary artery. The patient was referred for myocardial perfusion scintigraphy (MPS) to determine viability prior to surgical revascularization. MPS showed absent myocardial perfusion in the apex and apical anterior segments and thinned-out perfused myocardium in the midventricular to basal anterior segment and apical to basal inferior and lateral walls. This is consistent with markedly reduced perfusion in the segments supplied by the anomalous left coronary artery distribution. While echo cardiography and angiography are used to diagnose ALCAPA, the roles of MPS are to provide information regarding the viability of the areas supplied by the anomalous left coronary artery and to assess postoperative myocardial perfusion.