A 79-year-old man, who had undergone aortic valve replacement due to severe aortic stenosis 2.5 years previously and permanent pacemaker implantation for sick sinus syndrome 2 months after aortic valve replacement, was admitted for congestive heart failure and suspicion of prosthetic valve endocarditis. However, he had a fever in spite of medical therapy, and transthoracic echocardiography revealed a 20 mm vegetation on the posterior mitral valve leaflet. He underwent emergency surgery on a diagnosis of infective endocarditis. The intraoperative examination showed annular abscess on the calcified mitral annulus, and a part of abscess had disintegrated, from which the vegetation arose. We performed maximal possible debridement of the infected tissue and mitral annulus reconstruction with a bovine pericardium. Subsequently, mitral valve replacement and annulus reinforcement with a prosthetic valve collared with a bovine pericardium were performed to prevent perivalvular leakage. The patient showed no recurrence of infection and perivalvular leakage at 1.5 years of follow-up.