To the best of our knowledge, there have been no previous reports of chylothorax developing after pancreatectomy, although chylous ascites can occur. In patients with a pleuroperitoneal communication, ascitic fluid can flow into the thoracic cavity through a small hole in the diaphragm. A 70-year-old woman underwent total pancreatectomy and was referred to our department for treatment of right chylothorax after removal of her abdominal drainage tubes. An occult pleuroperitoneal communication was detected, and the portion of the diaphragm containing a diaphragmatic fistula was resected using a surgical stapler. After surgery, the chylothorax resolved, but chylous ascites developed. We speculated that this was a rare case of chylous ascites that flowed into the thoracic cavity through a diaphragmatic fistula after a pancreatic resection. When a patient develops chylothorax after an abdominal operation, the combination of a pleuroperitoneal communication and chylous ascites must be considered.