Two cases of leukemia were treated successfully with apheresis for delayed recovery of erythropoiesis due to antibody-mediated red cell aplasia after ABO-mismatched bone marrow transplantation (BMT). A 25-year-old female (ABO group O) underwent BMT from her brother (group A). Immunoadsorption using Biosynsorb A performed on day 146 after BMT followed by double filtration plasma pheresis (DFPP) reduced anti-A antibody titers from 1:32 to 1:2. Anemia improved dramatically within 2 weeks. A 49-year-old female (group O) underwent BMT from her mother (group A). She was treated with DFPP on day 131 after BMT. Anti-A antibody titers dropped from 1:16 to 1:1 and anemia improved gradually.