A 70-year-old man with severe chest pain was transferred to our hospital by ambulance. Computed tomography revealed a ruptured thoracic aortic aneurysm and massive bleeding into the posterior mediastinum. Emergency total aortic arch replacement was performed through median sternotomy. However sternal closure induced severe hypotension because the heart was elevated anteriorly by the posterior mediastinal hematoma. The hematoma could not be eliminated fully so the sternum was kept open at the first operation followed by delayed sternal closure 3 days after the operation. After that, the postoperative course was uneventful and the patient was discharged on postoperative day 43.