We experienced an autopsy case of who was discovered in a state of cardiopulmonary arrest and subsequently declared deceased due to severe pneumonia. Tests using a pan bacterial/viral detection kit and qualitative polymerase chain reaction (PCR) for Legionella pneumophila were negative. However, using deoxyribonucleic acid extracted from formalin-fixed paraffin-embedded lung tissue, PCR amplification of the ssrA gene of congeneric Legionella species yielded positive results. Histologically, slight staining was observed in the cytoplasm of macrophages in lung alveoli by Warthin-starry and Gimenez stains.