A 50-year-old man was admitted with respiratory failure. Chest X-ray and computed tomography revealed massive left pleural effusion and mediastinal shift. Pleural effusion showed abnormally high amylase levels of 42,600 IU/l and a high protein level of 3.2 g/dl. The serum amylase level was also 42,100 IU/l, and the proportion of pancreatic-type amylase was 88%. We diagnosed the patient with pancreatic effusion. Chest and abdominal enhanced computed tomography and magnetic resonance cholangiopancreatography revealed no pancreaticopleural fistula. He underwent a thoracoscopic examination that revealed brown pleural effusion as well as fibrin clots and thickness of the pleura. Histologically, there was no malignancy and the cause of pleural effusion was considered to be chronic pancreatitis.