A 53-year-old man with a penetrating trauma was admitted to our hospital. Thoracoabdominal computed tomography (CT) on admission showed left diaphragmatic injury and peritoneal fat in the left thoracic cavity. Under a diagnosis of the traumatic diaphragmatic injury, an emergency operation was performed, and the left diaphragm was repaired. No other injuries were found in the thoracic and abdominal organs by thoraco-laparoscopic observation. The postoperative course was uneventful, and the patient left hospital on the 14th day after surgery. In case of the diaphragm injury, it is important to confirm the probable injuries of other organs by thoraco-laparoscopic observation.