Mediastinal pancreatic pseudocyst is a rare complication of acute or chronic pancreatitis. It results from tracking of pancreatic fluid through diaphragmatic hiatus into the mediastinum. Herein, we report a case of mediastinal pancreatic pseudocyst in a 50-year-old man with a history of chronic pancreatitis. The patient complained of dysphagia and upper abdominal pain. Contrast enhanced computed tomography (CECT) revealed acute on chronic pancreatitis and a large posterior mediastinal pancreatic pseudocyst. CT guided drainage was performed and a repeat CT scan after seven days showed almost complete resolution of the pseudocyst. High index of suspicion is needed for the diagnosis. Mediastinal pancreatic pseudocyst is a rare entity and can cause serious complications if left untreated.