A 50-year-old woman with breast carcinoma metastases in the left supraclavicular region was treated because of free air in the mediastinum, around the heart and vascular pedicle, below the diaphragmatic dome, and subcutaneous neck and supraclavicular emphysema, without radiologic signs of pneumothorax. Diverticulosis of the colon and an occult perforation of the diverticulum in the retroperitoneal region of the colon were diagnosed. The patient was treated by segmental resection of the colon with anastomosis, drainage of the abdominal cavity, and antibiotics. To our knowledge, this is the only report in the literature about pneumopericardium caused by peridiverticulitis of the colon.