Bartonella spp are small Gram-negative rods, aerobic and highly fastidious. They are difficult to culture, in the routine bacterial cultures. They are considered as emergent human pathogens. Since 1993, three species of Bartonella (B. quintana, B. henselae, and B. elizabethae) have been described as causative agents of infectious endocarditis. In this paper we describe the case of a 43 year-old woman with a previous valvular heart disease, probably of rheumatic origin, owner of cats, that suffered an infectious endocarditis by Bartonella henselae in the aortic valve. This patient presented IgG titers against B. henselae of 1/4096 and against B. quintana of 1/256. She also had low IgM titers against B. henselae and B. quintana: 1/64 and 1/32, respectively. The patient received antibiotics for 12 weeks and suffered a valvular replacement due to the severe lesion on the aortic valve. On the endocardiac tissue of the removed valve DNA of B. henselae was detected (polymerase chain reaction-based assay). Clinical evolution of the patient was good. Diagnosis of Bartonella spp infection must be considered in every patient with infectious endocarditis and negative blood cultures, and particularly B. henselae in patients with previous valvular heart disease and regular contact with cats.