Abstract Background Pancreatic pleural effusion and ascites are defined as fluid accumulation in the thoracic and abdominal cavity, respectively, due to direct leakage of the pancreatic juice. They usually occur in patients with acute or chronic pancreatitis but are rarely associated with pancreatic neoplasm. We present here an extremely rare case of pancreatic neuroendocrine tumor with stenosis of the main pancreatic duct, leading to pancreatic pleural effusion. Case presentation A 51-year-old man complained of dyspnea. Left-sided pleural effusion was detected on the chest X-ray. Pleural puncture was performed, and the pleural fluid indicated a high amylase content (36,854 IU/L). Hence, the patient was diagnosed with pancreatic pleural effusion. Although no tumor was detected, the computed tomography (CT) scan showed a pseudocyst and dilation of the main pancreatic duct in the pancreatic tail. Magnetic resonance cholangiopancreatography showed a fistula from the pseudocyst into the left thoracic cavity. Endoscopic retrograde pancreatic drainage was attempted; however, it failed due to stenosis in the main pancreatic duct in the pancreatic body. Endoscopic ultrasound revealed a hypoechoic mass measuring 15 × 15 mm in the pancreatic body that was not enhanced in the late phase of contrast perfusion and was thus suspected to be an invasive ductal carcinoma. The patient underwent distal pancreatectomy with splenectomy and the postoperative course was uneventful. Histopathological examination confirmed a neuroendocrine tumor of the pancreas (NET G2). The main pancreatic duct was compressed by the tumor. Increased pressure on the distal pancreatic duct by the tumor might have caused formation of the pseudocyst and pleural effusion. To the best of our knowledge, this is the first case report of pancreatic pleural effusion associated with a neuroendocrine tumor. Conclusions Differential diagnosis of a pancreatic neoplasm should be considered, especially when a patient without a history of pancreatitis presents with pleural effusion.