We present a case of anomalous origin of the left pulmonary artery from a left-sided brachiocephalic artery via an arterial duct in a patient with a right aortic arch. Associated intracardiac anomalies were a large perimembranous ventricular septal defect and the persistence of a small vertical vein, connecting the pulmonary veins normally incorporated into the left atrium to the brachiocephalic vein. Spontaneous closure of the arterial duct occurred in the first days of life and was responsible for the circulatory “isolation” of the left pulmonary artery. The clinical course, surgical strategy and possible embryological explanation are described.