Primary malignant melanoma involving the nasal and paranasal sinus mucosa is a rare neoplasm, accounting for less than 1% of all melanomas. Being more aggressive than its cutaneous counterpart, it carries a poor prognosis. We report a case arising from the nasal septum mucosae in a 78-year-old man. We describe clinical features, diagnosis, and treatment of this rare disease along with a review of the pertinent literature. Endoscopic resection of the neoplasm was performed, enabling diagnosis of sinonasal mucosal melanoma involving the frontal sinus floor. Because the patient was too compromised to achieve radical surgical approach (craniofacial resection), he underwent radiation therapy. Through this article, we wish to emphasize that early diagnosis with a high index of suspicion is critical because this type of tumor is extremely aggressive. Its location and relatively nonspecific features frequently delay diagnosis, and its rarity avoids an optimal treatment guideline setting.