Hemitruncus arteriosus, anomalous origin of a pulmonary artery from the aorta, is a rare congenital heart disease frequently accompanied by other cardiovascular anomalies. In this case report, we present an exceedingly rare case of hemitruncus arteriosus in an 18-year-old male patient presenting with cyanosis and chest pain. Echocardiography raised a suspicion for aorto-pulmonary window; this was confirmed on cardiac computed tomography angiography. A magnetic resonance imaging study was performed for functional assessment. The resulting diagnosis was hemitruncus arteriosus with aberrant origin of the right coronary artery from the right pulmonary artery and unilateral absence of a pulmonary artery.