Serology has a key role in the diagnosis of infectious diseases in medicine. Bartonella henselae is a slow-growing, fastidious gram-negative bacillus, was first identified as a cause of endocarditis in 1993. It is responsible for approximately 6% cases of culture negative endocarditis. Serology, detection of DNA and cultures are utilized in the diagnosis of Bartonella infection. We faced an interesting situation where serology created more confusion than assisting the diagnosis.