Blastic plasmacytoid DC neoplasm (BPDCN) is a rare haematopoietic malignancy with an aggressive behaviour. We evaluated five patients allografted as consolidative treatment with an unrelated donor in first or subsequent remission. Four patients received a reduced intensity-conditioning regimen because of age or co-morbidities. As the stem cell sources, two umbilical cord blood-(UCB), two PBSC- and one BM graft were used. No GVHD was observed in the patients who received a UCB graft. However, both developed a post-transplant-associated lymphoproliferative disease. So far, only one patient has experienced relapse and was consecutively treated by escalated donor lymphocyte infusions (DLI). A potent graft-versus-leukaemia (GVL) effect was induced leading to a 17-month-long CR. Four patients are still in ongoing CR with median disease-free and overall survivals of 17 and 21 months. Thus, allogeneic SCT in BPDCN offers a potential curative option for patients with a compatible donor. UCB is an attractive alternative as a stem cell source. For relapsing patients, DLI can exert a powerful GVL effect.