We describe a patient who had received reduced-intensity stem cell transplantation (RIST) for metastatic renal cell carcinoma (RCC). A 37-year-old man developed rapid progression of RCC during steroid therapy for immune-mediated thrombocytopenia and graft-versus-host disease (GVHD). After discontinuation of corticosteroid, RCC achieved long stable disease with the presence of chronic GVHD, despite low dose of prednisolone. This case suggests the impact of immunosuppression on progression of metastatic RCC after RIST.