Cardiobacterium valvarum is a newly recognized human pathogen related to infective endocarditis. Cardiobacterium species are, however, only rarely the aetiology of infective endocarditis. An infective endocarditis case is presented and, additionally, phenotypic and phylogenetic comparison of a further 10 collection strains, representing the two species within the genus, was performed. C. valvarum was isolated from the blood and DNA was present in valvular tissue (partial 16S rRNA gene analysis) from a 64-year-old man with infective endocarditis of the mitral valve, rupture of chordae and prolapse of pulmonary valves in addition to a fluttering excrescence. A mechanical mitral valve and neochordae were inserted successfully. Phenotypically, the two species within the genus Cardiobacterium resemble each other greatly. When using the Vitek 2 Neisseria-Haemophilus identification card, the reaction for phenylphosphonate was positive for all Cardiobacterium hominis strains, but negative for all C. valvarum strains, thereby separating the two species. The two species made up two separate clusters by phylogenetic examination using 16S rRNA gene sequence analysis.