Ankylosis of the temporomandibular joint is a clinical entity that not only alters the normal anatomy of the face but also severely hampers mastication. Early diagnosis and treatment are crucial to prevent functional impairments and psychosocial conditions. Temporomandibular joint (TMJ) ankylosis is characterized by restrictions in movement due to intracapsular fibrous adhesions in capsular ligaments (fibrous ankylosis) and the formation of osseous masses resulting in articular component fusion (osseous ankylosis). Both types of ankylosis are mainly characterized by restrictions and/or limitations in mandibular movement and can originate from trauma, infection or systemic diseases. A case of unilateral complete temporomandibular joint bone ankylosis with bilateral coronoid elongation was observed in a 26-year-old woman seeking treatment for a facial deformity. A panoramic radiograph revealed an evident morphological abnormality on the left mandibular ramus. Cone-beam CT (CBCT) with 3-D construction was performed to confirm the diagnosis.