Abstract Xanthogranuloma (XG) is rarely observed in adults and has been reported to be associated with chronic myelogenous leukaemia (CML) and/or neurofibromatosis type 1 (NF1). A 68‐year‐old woman with adult T‐cell leukaemia/lymphoma (ATLL) gradually developed disseminated XGs over the 3 years since disease onset. Histopathological examination of a skin biopsy revealed the presence of histiocytes in the dermis with a few Touton giant cells admixed with lymphoid cells. The lesions of XGs persisted despite chemotherapy with prednisolone and chlorambucil for her ATLL. This is the first report of disseminated XGs associated with ATLL. The association of disseminated XGs with haematologic malignancies was reviewed and the possible pathogenesis of this association will be discussed.