Mitral valve aneurysm is a rare complication that may occur in a myxomatous valve. We report the case of a 73 year old male patient with severe mitral regurgitation and heart failure-class IV NYHA. Echocardiography showed perforation of an aneurysm of the anterior leaflet of the mitral valve associated with rupture of tendinous cords of the posterior mitral leaflet. Diagnosis was made by transthoracic echocardiography and confirmed by transesophageal echocardiography. The patient was urgently operated with success and a mitral valve prosthesis was implanted.