Many possible causes of resistance to human recombinant erythropoietin (rh-EPO) have been reported in patients with renal failure. This case presents an unusual cause of erythropoietin resistant anemia in a patient with chronic renal failure. A 61-year-old male patient who was on chronic hemodialysis program due to diabetic nephropathy for seven months developed erythropoietin resistant anemia. No iron deficiency was revealed by laboratory data, no megaloblastic anemia were found by biochemical investigation, and no inflammatory states including infection or neoplastic diseases were disclosed by abdominal ultrasonography, chest X-ray, bone marrow aspiration and biopsy, or other methods (normal C-reactive protein levels). This hemodialysis patient had epoetin-resistant anemia with primary autoimmune hyperthyroidism. The anti-thyroid therapy was effective not only against the hyperthyroidism but also against his epoetin resistant anemia.