We report an extremely rare case of spindle cell carcinoma of the sinonasal cavity. A 75-year-old man was admitted to our hospital because of right nasal obstruction. Nasal endoscopy showed a polypoid tumor measuring 3 × 3 cm at the nasal septum in the right nasal cavity, and an excisional biopsy was performed. Computed tomography (CT) demonstrated the nasal tumor extended to the maxillary sinus. Histologically, the tumor consisted of malignant spindle cells with hyperchromatic nuclei. Mitotic figures and necrosis were recognized. In some areas, edematous changes were recognized. No apparent differentiation was noted. The tumor cells were free of keratinization and intercellular bridge formations; therefore, there were no squamous cell components. Immunohistochemically, the tumor cells were positive for pancytokeratin, cytokeratin (CK)5/6, CK18, CK19, high molecular weight CK, p63, and vimentin. The tumor cells were negative for epithelial membrane antigen, CK7, CK14, p53 protein, S100 protein, HMB45, chromogranin, synaptophysin, CD34, CD56, glial fibrillary acidic protein, neuron-specific enolase, neurofilaments, α-smooth muscle actin, neuroblastoma, myoglobin, carcinoembryonic antigen (CEA), carbohydrate antigen (CA)19-9, CD3, CD20, CD30, CD45RO, and CD45. A pathological diagnosis of spindle cell carcinoma of sinonasal lesion was made. The patient underwent resection of right maxilla followed by chemotherapy and radiation and was alive without metastasis 5 years after initial presentation.