Although the survival rate for pediatric patients with hepatoblastoma has improved, prognosis is still poor when the disease is unresectable and refractory to chemotherapy. Therefore, novel approaches are warranted. Herein, we describe a patient with recurrent metastatic hepatoblastoma who received a nonmyeloablative hematopoietic stem cell transplantation from an HLA-matched unrelated donor. After withdrawal of immunosuppressant and establishment of full donor T-cell engraftment, the tumor regressed and serum α-fetoprotein level decreased in concurrence with the onset of graft-versus-host disease (GVHD). Her disease recurred when GVHD resolved. This patient's clinical course provides evidence for the probable existence of allogeneic graft-versus-hepatoblastoma effect. Pediatr Blood Cancer 2006, 46:501–505. © 2005 Wiley-Liss, Inc.