A solitary nasal schwannoma in a 31-year-old woman is described. The patient had a 10-year history of left nasal obstruction and presented with worsening symptoms. Computed tomography revealed a mass in the left nasal cavity extending into the ethmoidal and sphenoidal sinuses. A large, white polypoidal mass with a smooth surface was removed endoscopically piece by piece. Microscopic examination showed the tumor to be a benign spindle-cell neoplasm with predominantly mixed cellular pattern and with an indistinct focal mixture of hypercellular and hypocellular areas, likely representing Antoni A and B areas, respectively. Differential diagnoses included schwannoma, neurofibroma, solitary fibrous tumor, and meningioma. On immunohistochemical examination, the neoplastic cells showed diffuse and strong positivity for S-100. CD34 was positive primarily in the hypocellular area (Antoni B) but weak or negative in the hypercellular area (Antoni A). Staining for calretinin was focal and strong, and that for glial fibrillary acidic protein was diffuse and weak; however, stainings for estrogen receptor, epithelial membrane antigen, and α-smooth muscle actin were negative. This immunohistochemical profile confirmed the diagnosis of schwannoma. The combined use of immunostains (CD34, calretinin) could be useful for differentiating sinonasal schwannoma from its histological mimics when the typical features are weak or absent.