Temporomandibular joint (TMJ) ankylosis causes significant functional and aesthetic impairment. Treatment is often complex and results lack predictability. Among its multiple etiologies, trauma during infancy (often with undiagnosed lesions) may cause severe facial growth sequelae, including micrognatia. We report a case of an 8 year-old patient with bilateral TMJ ankylosis with sequelar micrognatia, with marked mouth opening limitation (1 cm), previously submitted to arthroplasty at age 4, but suffered recurrence. We performed bilateral mandibular osteogenic distraction (OD), according to an initial protocol of 1 mm/day (2 × 0.5 mm) which was adjusted to prevent laterognatia. A final growth of about 1.5 cm bilaterally was achieved, thus correcting the patient’s growth defect. Compliance was excellent which is of utmost importance for optimal outcome. Despite the clinical and symptomatic improvements obtained, treatment plan nevertheless includes TMJ reintervention, and orthognatic surgery. These procedures will likely be best succeeded due to the tissue growth already achieved. This case emphazises the risks of facial trauma in infancy, where a thorough diagnosis and close follow-up allow effective prevention and better outcomes. Our patient represents a severe case, with previous unsuccessful treatment, which required advanced and complex treatment, and illustrates the efficacy of OD for marked micrognatia.