Post-transplant erythrocytosis is an infrequent complication and has been reported after allogeneic hematopoietic stem cell transplantation (allo-HSCT) in aplastic anemia, acute myeloid leukemia, and chronic myeloid leukemia. The pre-disposing factors and treatment are not clearly defined. We present 11 post-transplant erythrocytosis cases. More studies should be conducted to distinguish the pathogenesis and follow-up for this rare complication.