While T-cell non-Hodgkin's lymphoma (NHL) associated with hemophagocytic syndrome (HPS) has been frequently observed, B-cell NHL associated with HPS has been rarely reported. We report a case of hepatosplenic B-cell lymphoma associated with HPS in a 41-year-old woman who presented with fever of unknown origin. An abdominal CT scan revealed splenomegaly with focal splenic infarction. Splenectomy and a liver wedge biopsy showed sinusoidal-pattern infiltration of medium to large tumor cells with positive reaction to a B-lymphocyte marker. Findings on bone marrow examination showed proliferation of histiocytes with avid hemophagocytosis.