The feasibility of adult-to-adult living donor liver transplantation (LDLT) is restricted by the adequacy of the graft size. A left lobe graft from a relatively small donor will not meet the metabolic demand of a larger recipient. We report a successful LDLT performed on a 90-kg man using an extended right lobe graft weighing 910 g from his relatively smaller-size brother. The donor-to-recipient body weight ratio was only 0.82. No homologous blood transfusion was required for the donor, and the donor recovered uneventfully except for mild transient hyperbilirubinemia. The graft provided adequate function for the metabolic needs of the recipient despite postoperative septic complications. Both donor and recipient were well with normal liver function at 4 months after operation. LDLT using the extended right lobe liver graft can extend the limit on the size of the adult recipient and may be a viable option even when the donor is relatively small compared with the recipient.