In tension gastrothorax, the abdominal contents are displaced into the thorax, leading to a mediastinal shift that arises from the pressureplaced on the intrathoracic region. This condition is often due to a congenital or acquired (secondary to surgery) diaphragmaticdefect and is rarely seen secondary to trauma. A 40-year-old man presented to the emergency department after an in-vehicle trafficaccident. He had no active complaint other than mild chest pain. On auscultation, breath sounds were audible in the left lung baseand bowel sounds were heard. Computed tomography of the thorax revealed left-sided diaphragmatic hernia. The jugular vein wasdistended, and the patient became desaturated in the emergency room. Nasogastric decompression was performed, and the saturationimproved. The patient underwent open surgery. Traumatic tension gastrothorax should be considered in the differential diagnosis ofacute-onset severe respiratory failure. It can be diagnosed by rapid clinical and radiological evaluation.