Cardiac herniation is a rare condition, which is often lethal in unrecognized cases. It is most commonly seen after pneumonectomy with associated pericardiotomy or pericardiectomy but has been reported in patients with iatrogenic, traumatic, and congenital pericardial defects. It is important that the radiologist be aware of this entity, as delay in diagnosis may be fatal. In this paper, we will discuss a case of cardiac herniation after right pneumonectomy and review the radiologic literature.