Our group describes a rare complication of inadvertent azygos vein cannulation during initiation of extracorporeal membrane oxygenation (ECMO) in a neonate with prenatal closure of the ductus arteriosus in a neonate born at an outlying facility and referred for possible congenital heart disease. Upon initial echocardiogram, no flow in the ductus arteriosus was present despite being maintained on prostaglandins. He necessitated ECMO support and the azygos vein was inadvertently cannulated. Lateral chest radiograph suggested placement of cannula in the azygos vein, and this was confirmed by echocardiography. Replacement of venous ECMO cannula with echocardiographic visualization of guide wire position restored ECMO flow. This report emphasizes the importance of lateral chest radiograph and prompt echocardiographic guidance at the time of ECMO cannulation particularly in clinical scenarios associated with azygos vein dilatation or elevated pressures in the right atrium or superior vena cava. Copyright © American Society of Artificial Internal Organs.