We describe the case of a 39-year-old Caucasian woman who was admitted to the University Hospital of Antwerp with a clinical picture suggestive of adult Still's disease. Even though a transoesophageal echocardiography showed endocarditis of the aortic valve, blood cultures remained negative. Additional serological testing revealed a positive result for Bartonella henselae. Histology of the supraclavicular lymph node showed a reactive lymph node with a positive polymerase chain reaction (PCR) for Bartonella henselae. Prednisolone treatment was started in a dosage of 10 mg per day and rifampicin 600 mg/d in combination with doxycyclin 200 mg/d was given for 6 months. During therapy the patient gradually improved and signs of endocarditis disappeared on echocardiography.