Immunosuppressive regimens that effectively prevent graft-versus-host disease (GVHD) after allogeneic blood or marrow transplantation (allo-BMT) have been associated with an increased incidence of post-transplantation lymphoproliferative disorder (PTLD) in the first year after transplantation. We evaluated the incidence of PTLD associated with the use of high-dose post-transplantation cyclophosphamide (PTCy) as GVHD prophylaxis. Between 2000 and 2011, a total of 785 adult allo-BMT recipients were given PTCy as GVHD prophylaxis at the Johns Hopkins Hospital, including 313 patients who received PTCy as sole GVHD prophylaxis. HLA-haploidentical or unrelated donor graft transplantation was performed in 526 patients (67%). No cases of PTLD occurred during the first year after allo-BMT in this series. PTLD is a rare occurrence after allo-BMT using PTCy, even in high-risk alternative donor transplantations.