We had experienced a case of traumatic myositis ossificans arising in right masseter muscle, inferior to zygomatic arch occurred on 25 year old male. He had some trauma on the site one year ago and visited with complaint of mouth opening limitation and swelling. Palpable mass with facial disfigurement was noted. and several ovoid radiopaque masses were revealed on C.T. examination. On histopathologic examination, multiple bone trabeculae with osteoblasts in its periphery was noted in connective tissues and invaded to neighbouring muscles, but any chondroid components were not revealed.