A case (4yrs old male child) of Langerhans cell histiocytosis (LCH) of right distal humerus presented with pain and swelling over lower third of right arm. X-ray showed osteolytic expansile lesion of right distal humerus involving metaphysis extending till metaphysio-diaphysial junction. Computed tomography (CT) revealed a large osteolytic expansile bony mass lesion involving lower end of humerus with eccentric cortical erosion and expansions of medullary cavity. Patient managed by Curettage of lytic lesion followed by G-Bone and autologous fibular bone grafting. Histopathological showed sheets of histiocytic cells which are ovoid cells with longitudinal groove and eosinophilic cytoplasm which are suggestive of Langerhans cell histiocytosis.