Erdheim-Chester disease (ECD) is a rare non-Langerhans cell form of histiocytosis that can affect the central nervous system. ECD predominantly affects adults, and only a few pediatric cases have been reported. The co-occurrence of ECD and Langerhans cell histiocytosis (LCH) is exceedingly rare. An 11-year-old boy, who was diagnosed with LCH 7 years previously, presented with multiple giant intracranial lesions. At the time of his initial diagnosis, only one intracranial lesion was observed, and it began to enlarge. Currently, up to 7 intracranial lesions can be observed in this patient. However, the diagnosis of ECD was not confirmed until this most recent open resection. The BRAF V600E mutation was detected in both LCH and ECD lesions. Dabrafenib therapy exhibited dramatic efficacy in this pediatric patient. This case represents the first successful application of dabrafenib in a pediatric patient with intracranial ECD lesions as well as mixed ECD and LCH. In this article, the authors describe the intricate diagnosis and treatment processes in this patient. Recent studies regarding treatment with BRAF inhibitors for neurological involvement in mixed ECD and LCH are also reviewed.