We report a case of a child with precursor-B acute lymphoblastic leukemia (ALL) who experienced refractory thrombocytopenia and massive splenomegaly during standard induction chemotherapy. He was diagnosed with hemophatocytic lymphohistiocytosis (HLH) during induction. Clinical and laboratory evaluation showed no evidence of infectious cause to HLH. Pancytopenia and HLH persisted after consolidation therapy even with remission from leukemia. After failure to control HLH with ALL-directed therapy and HLH-directed therapy, the patient underwent unrelated donor hematopoietic stem cell transplantation 8 months after diagnosis. He is 34 months post-transplant and in remission from leukemia and HLH. Pediatr Blood Cancer 2011;56:658–660. © 2010 Wiley-Liss, Inc.