Osteomyelitis of the temporomandibular joint (TMJ) is a rare disease that is characterized by osteitis of the mandibular condyle or glenoid fossa. Although this condition is usually associated with trauma, dental disease, or extension of a local infection, it may also occur as a complication of otologic infection. However, osteomyelitis of the TMJ as a complication of otologic surgery has not yet been reported. We present the case of a 54-year-old woman who developed a polyp on the superior portion of the tympanic membrane nine weeks after canal wall down mastoidectomy. This is an extremely rare case of a patient with osteomyelitis of the TMJ as a complication of otologic surgery.