Beckwith-Wiedemann syndrome (BWS) is a congenital growth disorder. Children born with BWS develop enlarged organs, including the tongue, a large body, and other signs. A woman with BWS was treated and followed for 30 years. Treatment consisted of tongue reduction, orthopedic and orthodontic treatment, orthognathic surgery, and retention. The patient was first treated when she was 5 years old. Her original orthodontic problems included macroglossia, anterior open bite, anterior crossbite, and a skeletal Class III jaw relationship caused by significant mandibular protrusion. The jaw-base relationships did not improve in the early preadolescent period after phase 1 of orthodontic treatment with a vertical chincap. With the growth spurt accompanying puberty, she developed a severe skeletal Class III jaw relationship and a constricted maxillary arch. Surgically assisted rapid maxillary expansion was performed at 23 years of age to correct the severe discrepancy between the maxillary and mandibular dental arch widths. Then, at 26 years, a LeFort I osteotomy, a horseshoe osteotomy, a bilateral sagittal split ramus osteotomy, and genioplasty were performed after presurgical orthodontic treatment with extraction of the mandibular first molars. Both the facial profile and the occlusion were stable after 6 years of retention. This case report discusses the result of long-term observation of a patient with BWS who underwent tongue reduction, early orthodontic treatment, and surgical-orthodontic treatment.