Acute myeloid leukemia (AML) is an extremely aggressive disease with a high relapse rate even after allogeneic hematopoietic stem cell transplantation (HSCT). We report the successful outcome of cell-mediated cytokine-activated immunotherapy in a high-risk pediatric AML patient who relapsed shortly after allogeneic HSCT. Donor lymphocyte infusion along with interferon induced a graft-versus-leukemia effect, presenting as a reversible episode of graft-versus-host disease, which led to stable complete donor chimerism and total eradication of AML for over 24 months, at the time of this report. The curative potential of immunotherapy in hematological malignancies is discussed.