Langerhans'cell histiocytosis (LCH) comprises a rare group of reticuloendothelial system disorders that can produce focal or systemic manifestations. Diabetes insipidus is considered to be an important indicator of serious underlying diseases in children, including LCH. We report the case of a young patient with monostotic LCH confined to the mandibular ramus, who was diagnosed with the disease after presenting symptoms of central diabetes insipidus and was satisfactorily treated with multi-agent chemotherapy. Additionally, we discuss the clinical, radiographic, histological and immunohistochemical findings, as well as the multidisciplinary approach of this important disease, which should receive attention by dental practitioners, especially when it occurs in children.