Viridans streptococci are the commonest cause of native valve infective endocarditis (IE). The taxonomy of this group is evolving allowing new disease associations to be made. Streptococcus vestibularis is a recently described member of the viridans group, first isolated from the vestibular mucosa of the human oral cavity. It has rarely been associated with human disease. Streptococcus oralis, another member of the viridans group resident in the human oral cavity is a well known cause of IE and bacteraemia in neutropenic patients. We report the first case of native mitral valve endocarditis due to S. vestibularis in a patient with co-existing S. oralis endocarditis.