A diaphragm is a musculotendinous partition that separates abdominal and thoracic organs and assists in ventilation. Three dogs were presented after being hit by a car, and one dog was presented with the history of respiratory problems including intermittent dyspnea and coughing. Survey thoracic radiography, positive contrast celiography and sonography revealed traumatic diaphragmatic hernia in three dogs and congenital peritoneopericardial diaphragmatic hernia in one dog. In three dogs including a dog with congenital peritoneopericardial diaphragmatic hernia, herniorrhaphy was performed. Among the three dogs underwent surgery, two dogs with traumatic diaphragmatic hernia recovered uneventfully. However the dog with congenital peritoneopericardial diaphragmatic hernia died from pulmonary edema at 2 days after surgery. Positive-contrast ceilography and ultrasonography provides to investigate the integrity of the diaphragm. Chronic diaphragmatic hernia and concurrent injuries are considered as prognostic factors.