A 60-year-old man was admitted for investigation of a mediastinal cystic lesion. During endoscopic retrograde pancreatography, the contrast medium leaked from the head of the main pancreatic duct, and the cystic fluid collected with endoscopic ultrasonography (EUS) -guided aspiration showed high levels of pancreatic enzymes. Therefore, we diagnosed mediastinal pancreatic pseudocyst. The pseudocyst shrank as a result of EUS-guided drainage, and an endoscopic nasopancreatic drainage tube was then placed to close the fistula of the pancreatic duct. This case suggests that endoscopic procedures could be useful for the diagnosis and treatment of mediastinal pancreatic pseudocyst. We review 48 case reports of mediastinal pancreatic pseudocyst and discuss the usefulness of endoscopic procedures for diagnosis and treatment.