Mycetoma of the paranasal sinus is defined as noninvasive fungal sinusitis and frequently occurs in immunocompromised hosts. Diagnosis of mycetoma is mainly based on histopathology because fungal culture tests are frequently negative. The maxillary and sphenoid sinuses are most often involved. We studied a large mycetoma of the maxillary sinus in a patient who was not immunocompromised but had previously undergone functional endoscopic sinus surgery. A large calcified blackbrown spore about 4 cm×4 cm×3 cm in size was detected over the right maxillary sinus. The calcified spore was cut into small pieces and removed endoscopically. Examination of the spore revealed many fungal hyphi with acute angles, which was compatible with aspergillosis. The condition did not recur during the two-year follow-up period.