Temporomandibular joint (TMJ) ankylosis is an extremely handicapping condition characterized by a permanent restriction in the ability to open the mouth, and it is mainly caused by traumatic and infectious events. It rarely occurs as a complication following orthognathic surgery. The treatment goals are the restoration of viable mandibular function and, in growing pediatric patients, symmetrical mandibular development. We are reporting here the unusual case of a bilateral bony TMJ ankylosis in a patient who underwent a bilateral sagittal split osteotomy of the mandible for correction of a mandibular deficiency. The patient was treated by bilateral arthrotomies with the interposition of a full-thickness skin graft as well as bilateral coronoidectomies with a favorable long-term (6 years) functional outcome. Only one similar case has been previously reported in the literature.