Pure red cell aplasia (PRCA) is a rare complication after ABO-incompatible allogeneic stem cell transplantation, but its mechanism is still unknown. Here we report on a patient with severe aplastic anemia who developed PRCA after HLA-identical but major ABO-mismatched peripheral blood stem cell transplantation. Erythroid engraftment was successful with primary steroid treatment. We concluded that an adequate dose of steroids can be the first line of therapy for PRCA after ABO-mismatched allogeneic stem cell transplantation.