We report a rare pediatric case of aggressive natural killer (NK) cell lymphoma, characterized by acute onset hepatosplenomegaly and respiratory distress, and infiltration by large granular lymphocytes with the phenotype of CD3-CD16-CD56+. The patient has remained in complete remission after short-pulse intensive chemotherapy, and myeloablative therapy followed by allogeneic bone marrow transplantation. We compare our case with 7 other children with NK cell leukemia reported from other institutions.