Neuroendocrine carcinoma (NEC) is rare. We report a case of probable sinonasal NEC in a 73-year-old man who had presented with a history of right nasal obstruction, nasal discharge, and recurrent epistaxis. On examination, a red, friable, gelatinous, polypoid mass with a tendency to bleed was seen in the right nasal cavity. Computed tomography revealed that the lesion was confined to the right nasal cavity; coincidental or reactive opacification was seen in the adjacent sinuses. The final histologic evaluation of the excised biopsy specimens yielded a diagnosis of an invasive, poorly differentiated NEC, probably a large-cell variant, with the differential diagnosis lying at a point somewhere between poorly differentiated large-cell NEC and high-grade olfactory neuroblastoma. The patient underwent a right lateral rhinotomy and medial maxillectomy followed by adjuvant radiotherapy. At 20 months of follow-up, he exhibited no sign of recurrence.