Donor cell-derived haematological neoplasms (DDHN) are rare disorders and currently do not have standardised diagnostic criteria and therapeutic management. International experts in allogeneic transplantation and haematological malignancies from Europe, the Americas, and Australia worked together on behalf of the EBMT Practice Harmonisation and Guidelines Committee to delineate a pragmatic diagnostic framework and issue guidance for downstream clinical management for DDHN. The team met on Sept 18-19, 2025, in Berlin, Germany, to discuss the definition, molecular insights, treatments, and donor outcomes for DDHN after an intensive review of the literature. In this Review, we present the epidemiology and clinical definitions of DDHN, provide guidance on diagnosis and prevention, address therapeutic considerations, and outline recommendations for donor management.