Myositis ossificans is a self-limiting ossifying process that most often develops following mechanical trauma to skeletal musculature. It chiefly affects the skeletal muscles of extremities of young athletically active adult males. Myositis ossificans is rare in children except for children affected by heritable disorder known as progressive myositis ossificans (fibrodysplasia ossificans progressiva). Children with this disorder develop ossification of muscles and associated soft tissue in early childhood without prior history of trauma. Traumatic form of myositis ossificans also known as myositis ossificans circumscripta (MOC) is rarely encountered in the head and neck musculature. We report a case of MOC within the buccinator which developed as a postoperative complication of mandibular third molar surgery. During extraction of a left mandibular third molar in a 16-year old male, a tooth fragment was accidently displaced into the adjacent soft tissue. Retrieval of this tooth fragment caused significant soft tissue trauma. Eighteen months after his third molar surgery, the patient continued to have pain and tenderness anterior to the left mandibular ramus. Radiographic imaging revealed a well-defined ovoid radiopaque mass within the left buccinator muscle. The lesion was surgically removed and the post-surgical course of the patient was uneventful. Histological findings of the mass were characteristic for myositis ossificans.