Postoperative hypoxemia can result from a variety of causes. We describe a case of platypnea-orthodeoxia caused by shunting across a patent foramen ovale in a 72-year-old woman immediately after a laparoscopic Nissen fundoplication procedure. This was diagnosed by echocardiography and treated successfully with percutaneous device closure. An intracardiac shunt should always be considered as a potential cause of refractory postoperative hypoxemia after procedures on the thorax and upper abdomen.