A ganglion cyst of the temporomandibular joint is a rare entity that commonly presents as a minimally tender, preauricular mass. This benign cystic lesion, which is lined by synovium and can be found in association with other joints, occasionally erodes adjacent bone to form an intraosseous ganglion. We discuss an unusual case of an intraosseous temporomandibular ganglion cyst that presented with bloody otorrhea. Examination revealed an external auditory canal mass with radiographic evidence of temporal bone erosion. The cyst was excised using a combined approach to the glenoid fossa and mastoid. The management principals of this case and a pertinent review of the literature are included.