We present in this paper a case of cardiac herniation following right intrapericardial pneumonectomy after induction chemotherapy. A 52-year-old man with advanced squamous cell carcinoma of the lung was admitted to our hospital suffering from a dry cough and chest pain. An intrapericardial pneumonectomy with partial pericardiectomy (4 x 4 cm) was performed. The pericardial defect was left open. Just prior to removal of the tracheal tube, cardiac herniation occurred with hypotension, arrhythmia and cardiac arrest. A chest X-ray revealed cardiac herniation into the right hemithorax. Re-thoracotomy was performed and the heart was returned to its normal position and the pericardial defect was immediately repaired with an expanded polytetrafluoroethylene (EPTFE) patch. The patient's postoperative course was uneventful. Unless prompt diagnosis and surgical treatment can be accomplished, cardiac herniation can be a fatal complication. We recommend that when pneumonectomy is performed, pericardial defects should be closed with a prosthetic patch, regardless of the defect's size.