Diaphragmatic hernia is usually congenital or follows thoracoabdominal injury. Diaphragmatic hernia combined with pneumothorax is a rare combination in the clinical setting, where pneumothorax is usually secondary to hollow viscera perforation in the long-term complications of diaphragmatic herniation or rupture of ectopic endometrium over the diaphragm during menstruation. Unlike the aforementioned conditions, we describe a 67-year-old man with chronic diaphragmatic hernia who suffered from pneumothorax and pneumoperitoneum secondary to pulmonary bulla by barotrauma during mechanical ventilation. Computed tomography showed scattered free gas in the thoracic and abdominal cavities, while there was no tenderness and rebound tenderness. The patient was managed conservatively with low PEEP and a lung-protective mechanical ventilation strategy. Finally, the oxygenation index gradually rose from 58 to 107. Unfortunately, in light of the patient’s poor clinical status and significant comorbidities, the patient passed away peacefully 3 weeks after hospital admission. Diaphragmatic hernia combined with pneumothorax should be differentiated from tension pneumothorax. Whether to intubate chest drainage depends on the cause of pneumothorax and pneumoperitoneum, as well as the risks and benefits of chest drainage. Additionally, mechanical ventilation should be applied cautiously, and respiratory parameters should be adjusted reasonably in patients at high risk of pneumothorax.