A 72-year-old man with chronic alcohol related pancreatitis was admitted for dyspnea and pain at the upper body. Chest X-ray showed right massive pleural effusion. Chest and abdominal contrast enhanced thin slice computed tomography revealed the route from the pancreatic head reaching the right thoracic cavity via the esophagus hiatus and the communication between the cystic lesion and main pancreatic duct. We drained the pleural effusion that showed abnormally high amylase activity. We diagnosed his illness as mediastinal pancreatic pseudocyst with pancreatic pleural effusion. Endoscopic Nasopancreatic Drainage catheter was placed in the main pancreatic duct, and the pleural effusion disappeared.