Proteus syndrome is a congenital hamartomatous malformation that is characterized by a wide range of deformities, including craniofacial deformities. Proteus syndrome features partial gigantism and asymmetry of the limbs, plantar hyperplasia, hemangiomas, lipomas, lymphangiomas, varicosities, verrucous epidermal nevi, macrocephaly, cranial hyperostosis, and long bone overgrowth. We diagnosed Proteus syndrome in a male patient who visited our hospital with a chief complaint of limited mouth opening and report the case because we obtained a good healing outcome after treating the condition with a corrective osteotomy.