Budd-Chiari syndrome (BCS) results from diverse causative factors. Myeloproliferative disorders (MPDs) including essential thrombocythemia (ET) account for a minority of BCS cases in Japan. ABO-blood-type incompatible living donor liver transplantation (LDLT) in adults has become an acceptable procedure owing to the development of new strategies for preventing antibody-mediated rejection. This report presents a rare case of BCS secondary to ET, which was cured by an ABO-incompatible (AB to A) LDLT. In this case, prostaglandin E(1) and gabexate mesilate were administered into portal vein and rituximab prophylaxis was applied. No splenectomy was performed as it is in most ABO-incompatible cases, since a flow cytometry showed no anti-B antibodies in the splenocytes collected by a wedge biopsy during the LDLT. The postoperative course was uneventful. Anti-coagulation therapy was initiated with aspirin and warfarin instead of hydroxyurea. This report describes an ABO-incompatible LDLT without a splenectomy for BCS secondary to ET.