Acute renal failure is the most common complication of rhabdomyolysis. However, hyperosmolar hyperglycemic state (HHS) induced-rhabdomyolysis rarely causes acute renal failure (ARF) because HHS induces osmotic diuresis and prevents tubular necrosis. Here we report a case of acute renal failure caused by HHS-induced rhabdomyolysis in a patient with poorly controlled diabetes mellitus. A 59-year-old male was admitted with comatose mentality. He had been diagnosed with diabetes mellitus 6 months ago but had not been treated. Physical examination showed severe dehydration of oral mucosa. His laboratory findings demonstrated severe HHS, rhabdomyolysis and acute renal failure (plasam glucose 1,543 mg/dL, osmolarity 329 mOsm/L, creatine phophokinase 15,395 IU/L, lactate dehydrogenase 1,046 IU/L, creatinine 2.4 mg/dL). With adequate hydration and insulin therapy, HHS improved but rhabdomyolysis and ARF were more aggravated. With early hemodialysis treatment, he finally improved without sequale.