Total anomalous pulmonary venous return (TAPVR) is a rare congenital heart defect that occurs when all four pulmonary veins connect to the systemic venous circulation. We describe a full-term male neonate who presented with cyanosis and mild tachypnea shortly after birth. One umbilical artery and the umbilical vein were catheterized, and oxygen treatment was provided. Four echocardiograms indicated severe pulmonary hypertension and were negative for any congenital heart defects. After the umbilical artery catheter was removed, high partial pressure of oxygen was detected in blood samples drawn from the umbilical venous catheter that was positioned below the diaphragm. Based on this finding, TAPVR was suspected and confirmed with angiography through a central venous catheter. The neonate underwent a successful surgical repair to correct the cardiac defect.