The Authors report a case of gastric perforation into the left pleural cavity due to the herniation of the gastric fundus into the thorax in a patient who suffered from a thoraco-abdominal trauma four months before. A few physiopathological aspects of post-traumatic rupture of the diaphragm with a delayed presentation are discussed. Clinical and radiological typical elements of the chronic undiscovered diaphragmatic herniation are underlined and the events related to the complications (strangulation, perforation) are described. Finally, a few therapeutical principles are discussed.