Outpatient drainage therapy is generally indicated for spontaneous pneumothoraces. A 63-year-old man, who had been attacked by a bull sustaining injuries on the right side of his chest, was referred to the emergency room with dyspnea. His chest X-ray showed a small pneumothorax. The next day, a chest X-ray demonstrated that his pneumothorax had worsened, although no hemothorax was identified. Outpatient drainage therapy with a thoracic vent was initiated. The air leak stopped on the third day and the thoracic vent was removed on the sixth day. Thoracic vents can be a useful modality for treating traumatic pneumothorax without hemothorax.