Ankylosis of temporomandibular joint is a condition in which partial or complete immobilization of mandible occurs because of fusion between mandibular condyle and skull base. This condition can be treated orthodontically, surgically, or therapeutically or by prosthodontic rehabilitation. A 10-year-old female patient presented to the Department of Oral and Maxillofacial Surgery, Gazi University Faculty of Dentistry, with limited mouth opening. She got injury in the face when she was 5 years old. Extraoral and intraoral examination findings were facial asymmetry on the left side, micrognathic mandible, and 19-mm mouth opening. After radiographic examination, ankylosis (Shawney type I) on the left side was revealed, and the patient was referred to Department of Orthodontics. After orthodontic clinical examination, we create following multidisciplinary treatment approach: (1) acrylic posterior bite block with spring application, (2) interpositional arthroplasty operation, and (3) physiotherapy (passive mouth-opening exercises). After the follow-up of 9 months, significant improvement (5 mm) was noticed in the opening of the mouth, and we decided to remove appliance and operate on the patient. Surgical procedure was performed under general anesthesia via blinded nasotracheal intubation. To prevent postoperative relapse, temporal fascia was interpositioned and sutured. Passive mouth-opening exercises were started 10 days after the surgery. Thirty-one-millimetermouth opening was reached after the surgery and passive mouth-opening exercises. Patient's routine controls have been continued for 2 years.