INTRODUCTION: Mitral annular calcification is a common finding in elderly patients; it is considered a benign cardiac abnormality but it can be a predisposing factor for infective endocarditis. Although described in numerous necropsy studies, endocarditis on mitral annular calcification has rarely been reported during life, and the frequency of sepsis can be underestimated because of difficult diagnosis. CASE PRESENTATION: We present a case of infective endocarditis on mitral annulus calcification in a patient with acute coronary syndrome, diagnosed with transthoracic echocardiography. CONCLUSION: Transthoracic echocardiography may contribute to a correct diagnosis, showing typical findings of infective endocarditis on mitral annular calcification in order to administrate an adequate antibiotic prophylaxis in patients undergoing endoscopic or invasive procedures.