We describe a patient with typical hemophagocytic syndrome (HPS) in whom pancytopenia was refractory to steroid pulse therapy. He was successfully treated with immunosuppressive therapy using antithymocyte globulin (ATG) and cyclosporine (CyA), which is known to be effective for aplastic anemia (AA). Activation of histiocytes occurs in HPS as a response to several cytokines produced by activated T lymphocytes, while apoptosis of hematopoietic stem cells in AA is caused by T lymphocyte-derived cytokines. The response of this patient indicated that both diseases may have some similar immune-mediated conditions involving the activation of T lymphocytes and that intensive immunosuppressive therapy with ATG and CyA might be a useful strategy for steroid-resistant HPS.