Septic arthritis due to Salmonella has been reported frequently, but multiple joint involvements have rarely been reported in children. A 3-year-old girl presented with Salmonella arthritis involving multiple joints. Laboratory investigations revealed pancytopenia inconsistent with diagnosis of juvenile rheumatoid arthritis or septic arthritis. Bone marrow examination 2 weeks later confirmed the diagnosis of acute lymphoblastic leukemia (ALL). Immunophenotyping studies were consistent with a diagnosis of pre-B ALL. This case illustrates that a delay in the diagnosis may occur when there is an apparent infection focus without classic features of leukemia. Multiple joints involvement of septic arthritis associated with pancytopenia should highlight the possibility of underlying hematologic disorders.