Lactobacillus sp., generally considered to be a harmless indigenous bacteria of the mucous membrane, occasionally causes serious infections. Lactobacillus endocarditis is a very rare disease, and no case has been reported in Korea. Gram-positive bacilli were isolated from blood cultures of a 41-year-old man with clinically suspected subacute bacterial endocarditis. The patient had a dental procedure 3 months prior to the infection. The isolate was identified as L. casei subsp. casei based on the cultural characteristics and gas liquid chromatography of metabolic products. The patient was treated with ampicillin and improved. When Lactobacillus is isolated from the blood of an endocarditis patient, the significance should be seriously considered.