Anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) is a rare congenital defect that presents even less frequently in adults. Here we described a 40-year-old patient presenting with palpitations. Electrocardiography revealed frequent ventricular ectopy. Echocardiography revealed a dilated left ventricle and an abnormal flow pattern in the pulmonary artery and at the right side of the interventricular septum. Coronary angiography demonstrated an enlarged right coronary artery (RCA) with collateralization to the left coronary artery (LCA) and reflux of contrast into the pulmonary artery. Computed tomography confirmed ALCAPA syndrome. Surgical corrections were planned.