Hemophagocytic lymphohistiocytosis (HLH) is a severe and life-threatening condition causing multisystem involvement such as cytopenia, hepatosplenomegaly, and death. Dengue infection is one of the leading causes of HLH. We reviewed three cases of children at HRH Princess Maha Chakri Sirindhorn Medical Center, Faculty of Medicine, Srinakharinwirot University, Nakhon Nayok, Thailand, with dengue fever who subsequently developed HLH, based on the HLH-2004 diagnostic criteria. Following treatment with dexamethasone and intravenous immunoglobulin, there was a dramatic response including defervescence and improvement of cytopenia, hyperfibrinogenemia, and hyperferritinemia. Key features for diagnosis of dengue fever complicated by HLH include a history of prolonged fever exceeding seven days, splenomegaly, and worsening cytopenia. Early recognition and treatment are crucial for a successful outcome.