A 34-year-old man, working at a park in Tokyo, Japan, was repeatedly bitten by mosquitoes while cutting grass. He was hospitalized with sudden fever, fatigue, and weakness. He was eventually diagnosed with dengue virus infection, detected using reverse transcription polymerase chain reaction for the genome and by the presence of nonstructural protein 1 in his peripheral blood. Symptomatic treatments such as acetaminophen for the fever were not effective. Moreover, peripheral blood examination showed drastically decreased white blood cells and platelets, as well as marked elevations of ferritin and soluble interleukin 2 receptor. Furthermore, bone marrow examination revealed increased macrophages with hemophagocytosis. Dengue infection with hemophagocytic lymphohistiocytosis (HLH) was ultimately diagnosed. Half-dose steroid pulse therapy for three days dramatically reduced his temperature, thereby ameliorating physical symptoms and restoring normal peripheral blood data. He was discharged 12 days after admission. Dengue infection with HLH is rare and this is the first report, to our knowledge, of domestic dengue infection with HLH in Japan. Early steroid therapy may be effective in such cases.