Hypoglossia-hypodactyly, or aglossia-adactylia syndrome with or without limb anomalies, is an extremely rare congenital condition. It is characterized by a narrow, V-shaped mandibular dental arch with micrognathia, and is typically challenging to treat. We have previously reported 3 patients with hypoglossia-hypodactyly syndrome without limb anomalies who were treated with transverse distraction osteogenesis at the mandibular symphysis during childhood. In this report, we present the long-term prognoses of these 3 cases, until 18 years of age. Of the 3 total cases, sufficient and stable results in occlusion, speech, mastication, and facial appearance were obtained in 2 cases with subsequent orthodontic treatments. Similar results were not observed in the remaining case when continuous orthodontic treatments were not performed. Based on these results, we propose that the transverse distraction osteogenesis procedure at the mandibular symphysis during childhood could be a reliable method to correct the V-shaped mandibular arch of hypoglossia-hypodactyly syndrome, when subsequent orthodontic treatments are provided during the patient's growing period.