Hemolytic Uremic Syndrome (HUS) is the most common cause of acute renal failure in children and is comprised of the combination of hemolytic anemia, thrombocytopenia, and acute renal failure. Atypical HUS, rare in childhood, has worse prognosis than that of typical HUS and is associated with chemotherapy drug, other bacterial (especially Streptococcus pneumoniae) or viral infections, and so on. We report a case of HUS caused by pneumococcal infection in 4-year-old boy. While he was admitted with pneumonia and pleural effusion, pneumococcal infection could be revealed. Although HUS progressed rapidly, he immediately received 3-time hemodialysis and recovered completely after two weeks.