A case of unilateral ankylosis of the temporomandibular joint, which caused micrognathia with facial asymmetry, was reported. A 3-year-old female visited our department because of facial asymmetry She was placed on conservative therapy using a functional appliance to improve facial asymmetry and occlusal relationship. Because of mandibular trismus, condylectomy was performed at the age of 13 years 10 months. Interincisal distance increased to 38mm, but micrognathia with facial asymmetry remained. Therefore, Le Fort I osteotomy combined with extraoral vertical ramus osteotomy on the affected side and sagittal split ramus osteotomy on the opposite side was performed at the age of 16 years 10 months. In addition, augmentation genioplasty with a porous hydroxyapatite block was performed at the age of 17 years 6 months. Four years later, the patient was satisfied with recovery of jaw opening and improvement in facial appearance.