Infective endocarditis is the infectious disease that produces vegetation on endocardium. Acute bacterial endocarditis is most frequently caused by Staphylococcus aureus, occurs on a normal heart valve, and subacute endocarditis usually caused by Streptococcus viridans occurs on damaged valves. Gemella haemolysans are gram-positive cocci that is placed in the family Streptococcaceae. As opportunistic pathogen, Gemella haemolysans are able to cause severe localized and generalized infections and it is known that this organism very rarely causes infective endocarditis. The paucity of reports concerning Gemella haemolysans is probably related to the difficulties associated with their identification. Several laboratory tests to prevent misinterpretation of this organism are now suggested. We have experienced a case of infective endocarditis that is caused by Gemella haemolysans in 37 year old male patient with ventricular septal defect. Gemella haemolysans were detected by blood culture and he was treated with intravenous vancomycin with gentamicin and ceftriaxone, and also underwent cardiac surgery. This is the first case of Gemella haemolysans endocarditis of ventricular septal defect in Korea.