We experienced a case of left traumatic diaphragamatic hernia accompanied with rupture of pericardium after blunt trauma by traffic accident. A 55-year-old man who had suffered blunt chest and upper abdominal trauma because of smash of two cars when he had been turning to right in the corner was admitted to our hospital. On arrival at the hospital, the patient complained severe dyspnea that reduced by lying on his right. Another position couldn't be taken because of deterioration of dyspnea. Chest X-ray showed disappeared left diaphragmatic line and abnormal transparent mass that suggest alimentary canal in the left intrapleural space. Cardiac ultrasonography showed abnormal tubular mass close to the left side of mediastinum that deviated to right. The patient was diagnosed as traumatic diaphragmatic hernia and emergency operation was performed. Left diaphragma was lacerated sagitally toward its top for about 12 cm in length. Left pleuropericardium was seen to be lacerated longitudinally for about 8 cm in length in front of the phrenic nerve intraoperatively. Both lacerations were closed by direct suture. The patient discharged on the 37th postoperative day without phrenic nerve palsy. At making diagnosis of patient with chest and abdominal trauma, injure of diaphragma and/or pericardium also must be considered. If it is possible, operation must be performed without hesitation in order to get good prognosis.