Tension gastrothorax is a very rare but potentially fatal clinical condition in which the stomach that herniates through a diaphragmatic defect into the thorax is massively distended by trapped air. It leads to severe symptoms due to the compression of the lung and mediastinum. A 27-year-old female, who had no prior trauma history, applied to the emergency service with the complaint of respiratory disorder, and was consulted by the department of thoracic surgery. Thorax CT revealed presence of gastrothorax in the left hemithorax. Thus, the patient went into cardiopulmonary arrest and was resuscitated. Emergency thoracotomy was performed, abdominal organs were reduced and diaphragmatic defect was repaired. She was discharged on the fifth postoperative day without any complications.