Introduction: Hemophagocytic lymphohistiocytosis (HLH) is a syndrome characterized by fever, pancytopenia, splenomegaly, and hemophagocytosis in bone marrow, liver, or lymph nodes. Laboratory findings include hypertriglyceridemia, hyperferritinemia, and hypofibrinogenemia. The symptoms of HLH are generally rapid and often lead to life-threatening conditions. It can be classified as primary or secondary HLH. Secondary HLH is associated with infections, autoimmune disease or malignancies. We report a case of HLH in a 5-year-old girl due to group B streptococcus (GBS) sepsis. Case report: A 5-year-old girl was admitted to the emergency room with fever and cyanosis. She had no past or familial history. The fever and myalgia started 2 days ago, and then vomiting, cyanosis, and bilateral edema occurred 2 hours before admission to emergency room. The vital signs were heart rate 170 times/min, unmeasured blood pressure, body temperature 38°C, respiratory rate 50 times/min, and oxygen saturation 85%. On physical examination, she had splenomegaly, systemic cyanosis and bilateral leg edema. Hematologic studies showed leukocytosis (18,050/μL) and thrombocytopenia (73,000/μL). Other laboratory abnormalities were observed with C-reactive protein 410 mg/L, procalcitonin 40.3 ng/mL, ferritin 6,599 ng/mL, triglyceride 655 mg/dL, aspartate aminotransferase/alanine aminotransferase 319/99 IU/L, total bilirubin/direct bilirubin 4.7/3.6 mg/dL, and blood urea nitrogen/creatinine 75/2.7 mg/dL. Fibrinogen level was 50 mg/dL. Under the impression of septic shock and HLH, mechanical ventilator care, intravenous hydration, inotropics, and empirical antibiotics (teicoplanin and meropenem) were administered. At the same time, packed red blood cell, platelet, and fresh frozen plasma were transfused, and intravenous immunoglobulin administered. Nevertheless, her blood pressure was not maintained and cardiac arrest occurred. Despite cardiopulmonary resuscitation, she has expired. There were no serological evidence of viral infections and autoimmune disease. After she died, GBS was identified in two blood cultures. Conclusion: We report 5-year-old girl who died HLH caused by GBS sepsis without any past medical history.