Herein, we present a case of coexisting neuroendocrine carcinoma and conventional adenocarcinoma (collision tumor) in the ampulla of Vater, which has seldom been reported in the literature. A 51-year-old man presented with a month history of jaundice. MRCP disclosed about 1.9×1.8 cm sized heterogeneously enhancing mass in ampulla of Vater, causing obstructions of distal common bile duct. He underwent pylorus-preserving pancreaticoduodenectomy under the diagnosis on ampulla of Vater cancer. Pathologically, sections on the ampulla of Vater showed conventional ductal adenocarcinoma extended and collided with poorly differentiated neuroendocrine carcinoma. In conclusion, we hereby presented a case of coexisting neuroendocrine carcinoma and conventional adenocarcinoma in the ampulla of Vater.