The authors report a 57-year-old male patient who presented with diarrhea, darkened urine, jaundice and increased blood urea nitrogen and creatinine. Initially, his symptoms, which included hemolytic anemia, acute renal failure and low platelet count, seemed to be caused by renal injuries associated with thrombotic microangiopathy, hemolytic-uremic syndrome in particular. However, a renal biopsy indicated acute tubular necrosis and hemosiderin deposition. A CD55 and CD59 assay, Ham test and sugar-water hemolysis test confirmed the diagnosis of paroxysmal nocturnal hemoglobinuria. After fluid infusion, diuresis and urine alkalization, the patient gradually regained nearly normal renal function. This case illustrates that paroxysmal nocturnal hemoglobinuria may present with acute kidney injury when hemolysis, diarrhea and hemosiderin deposits in the renal tubular epithelial cells and renal tubules are present. Early diagnosis and treatment is crucial to prevent disease progression and irreversible chronic renal failure.