Respiratory syncytial virus (RSV) is a common cause of respiratory tract infection in children. Although previously considered as children's virus, the increasing number of patients who receive immunosuppression after transplantation of bone marrow and solid organs highlighted the role of RSV as a pathogen for opportunistic infection. We report a case of community-acquired respiratory syncytial virus pneumonia in a patient with newly diagnosed leukemia, resulting in acute respiratory distress syndrome (ARDS).