We report a fatal case of Waterhouse-Friderichsen syndrome in a 64-year-old man. The diagnosis, suspected during the autopsy (performed 63 hours after death), was confirmed through the successful detection of Streptococcus pneumoniae DNA and antigens in samples (blood and liver) collected during the autopsy. These results conformed with blood cultures performed antemortem, which became available only the day after the autopsy. The case underlines the need to collect biological material (liver and blood samples) during autopsy for microbiological investigations, although the collection is performed a long time after the death, suggesting that a liver sample works for DNA and liver and blood work for Streptococcus pneumoniae antigen detection.