Legionella endocarditis is extremely uncommon, and embolic phenomena have never been reported. We report the first case of Legionella micdadei prosthetic valve endocarditis complicated by brain abscess. A 57-y-old immunocompromised woman with a history of mitral valve replacement developed confusion and left-sided weakness. Brain magnetic resonance imaging showed a 3-cm peripheral-enhancing mass. Transoesophageal echocardiography suggested a perivalvular abscess. Blood cultures and valve cultures were negative. She was diagnosed with 16S rRNA polymerase chain reaction and silver stain, and was discharged with levofloxacin after a redo mitral valve replacement. Twelve cases of Legionella endocarditis were reviewed. Only one case had a native valve, and her endocarditis occurred after pneumonia. All cases were cured. The duration of antibiotic therapy was variable. Legionella species should be considered in the differential diagnosis of culture-negative endocarditis in both immunocompetent and immunocompromised patients. Molecular techniques and silver impregnation stains are useful, especially when cultures using buffered charcoal-yeast extract agar are negative.