A neonatal case of legionnaires' disease (LD) is reported. A male neonate was admitted to our hospital with high fever and dyspnea, which had started 5 days after birth, and died due to severe pneumonia at 10 days old. An autopsy revealed small areas of granular consolidation scattered diffusely in the bilateral lungs. Microscopic examination of the lungs showed mainly lobularly distributed pneumonia. Extensive exudation of macrophages and neutrophils was observed in the terminal respiratory tract and alveolar spaces. Warthin-Starry and Gimenez staining and electron microscopy detected many coccobacilli in the cytoplasm of exudated macrophages and neutrophils. Immunofluorescence staining using antiserum against Legionella pneumophila, serogroup 1, showed a positive reaction. Bacteriological examinations of aspirate from the respiratory tract and autopsied lung tissue confirmed the presence of Legionella pneumophila, serogroup 1. Extrapulmonary LD was not detected. LD usually affects aged or immunocompromised hosts, but there was no evidence of immune deficiency in this case. Pediatric cases of LD have rarely been reported, and a survey of the literature revealed few neonatal cases. The present case may alert neonatologists and other medical personnel to the possibility of neonatal LD infection.