Hand, foot, and mouth disease (HFMD) is an acute, mostly self-limiting infection that recovers without any sequelae. However, a few cases are life threatening, especially those caused by enterovirus 71. We report a 12-month-old boy with enterovirus 71–infected HFMD who presented with sudden-onset massive pulmonary hemorrhage and suspected encephalitis. He was admitted to a primary hospital with high fever and vesicular lesions on the mouth, hands, and feet. After 3 days, he experienced 3 episodes of convulsions and was referred to our hospital. He was conscious and his chest radiograph was normal on admission. However, he suddenly became unconscious 6 hours later and massive pulmonary hemorrhage occurred. He experienced several convulsions intermittently. Chest radiography revealed diffuse infiltrations in both lung fields. Intravenous immunoglobulin, dexamethasone, cefotaxime, leukocyte-depleted red blood cells, fresh frozen plasma, inotropics, vitamin K, and endotracheal epinephrine were administered. He expired 9 hours after intubation, within 3 days from fever onset. Retrospectively, enterovirus 71 was isolated by real-time RT-PCR from his serum and nasopharyngeal swab.