A primary extra-ampullary duodenal neuroendocrine carcinoma was found in a 40-year-old man who presented with upper abdominal pain and weight loss. Duodenoscopy and hypotonic duodenography revealed a protruding fungating mass with luminal occlusion at the third part of the duodenum (D3). Although the metastatic work-up was normal, the tumor was inoperable intraoperatively, hence a palliative bypass was carried out followed by chemotherapy with 5-fluorouracil and leucovorin. Examination of the biopsy by immunohistochemistry and ultrastructural study revealed it to be neuroendocrine in nature, expressing synaptophysin, chromogranin and cytokeratin and containing dense core cytoplasmic granules. However, there was no evidence of clinical endocrinopathy. The present case emphasizes the need for better detection, further analysis and evaluation of such rare cases to identify their clinical course and effective treatment modalities.