Leuconostoc lactis, often found in fermented dairy products, although considered to have a low pathogenic potential, can cause life-threatening infections in immunocompromised hosts. We herein report a 62-year-old man with a history of alcoholic liver cirrhosis, hepatocellular carcinoma, and diabetes mellitus who developed a very rare case of bacterial meningitis caused by this organism. After we administered antibiotics including ampicillin, he recovered completely within two weeks. This gram-positive coccus (GPC) is sensitive to ampicillin but naturally resistant to vancomycin, while its susceptibility to ceftriaxone has not yet been established. In acute GPC meningitis in immunocompromised hosts, Leuconostoc lactis should therefore be considered as a possible pathogen.