A 62-year-old man who had suffered fractures of the left chest wall and hemothorax 1 year earlier was admitted to our hospital with multiple injuries as a result of a traffic accident. Chest drainage was immediately performed under the diagnosis of left hemothorax followed by immobilization of fractures of the femur and radius. On the second day after admission, he suddenly developed severe chest pain and dyspnea after sitting up in bed. Echocardiography and chest computed tomography (CT) showed herniation of the left ventricle into the left thoracic cavity, whereby a diagnosis of cardiac herniation due to rupture of the pericardium was made and an emergency surgical repair was successfully performed. Only eight cases of patients surviving after traumatic cardiac herniation have been reported in Japan; however, this is the first in which a preoperative diagnosis was made by echocardiography and chest CT scanning prior to surgical repair.