Blastic plasmacytoid dendritic cell neoplasm (BPDCN) is an extremely rare condition that originates from dendritic cells. We report on the first case of Epstein-Barr virus (EBV)-driven post-transplant lymphoproliferative disorder (PTLD) of donor origin in a BPDC patient post-allogeneic haematopoietic stem cell transplantation (HSCT). Flow cytometry study identified a cell population CD4+/CD56+/CD45RA+/CD123+/TCL1+ suggestive of BPDCN diagnosis, which was confirmed by a lymph node biopsy (cells positive for BCL11a, BDCA-2, CD2AP, CD123, TCL1 and S100). Cytogenetic analysis revealed a complex karyotype: (19 metaphase) 47,XX,t(1;6)(q21;q2?5),-13 + 2mar[11]/47, XX, +21 [3]/46,XX [5]. The patient was started on acute myeloid leukaemia (AML) induction schedule, and subsequently an allogeneic HSCT was performed. On day +36 post-HSCT, bone marrow biopsy/aspirate showed complete morphological remission, and chimerism study showed 100% donor chimera. However, on day +37, the patient was found to have enlarged cervical and supraclavicular lymphoadenopathy, splenomegaly and raised lactic dehydrogenase. EBV-DNA copies in blood were elevated, consistent with a lytic cycle. A lymph node biopsy showed EBV encoded RNA and large atypical B cells (CD45dim-, CD4+/CD56+, monoclonal for k-chain, CD19+/CD20+/CD21+/CD22+/CD38+/CD43+/CD79β-/CD5-/CD10-), consistent with PTLD monomorphic type. Chimerism study showed that PTLD was of donor origin. This case together with the recent literature findings on BPDCN and PTLD are discussed. Copyright © 2012 John Wiley & Sons, Ltd.