Hematopoietic cell transplantation corrects a hematological phenotype of Diamond-Blackfan anemia (DBA). Reduced conditioning has been recommended for patients with the cancer predisposition, but appropriate intensity is required to prevent graft failure. We conducted unrelated-donor bone marrow transplantations in six consecutive transfusion-dependent patients (median age, 5.4 years; range, 1.8–23) after targeted-busulfan (60–75 mg/L×h of cumulative AUC) and fludarabine regimen without irradiation. All obtained chronic graft-versus-host-disease-free complete donor chimerism, including one unrelated cord blood transplantation rescue. The rescued 7-year-old girl had the longest transfusion-dependency (>40 months) and highest ferritin level (>2,000 ng/mL) pretransplant. Intermediate-intensity targeted busulfan-based conditioning may cure DBA.