Escherichia coli is a rare cause of infectious endocarditis. We report a clinical case of E. coli endocarditis of a native mitral valve in a young 26-year-old woman with a recurrent urinary tract infection who had a high fever for one week despite probabilistic treatment with amoxcillin-clavulanic acid 3 g per day. The patient was successfully treated with antibiotics and recovered without surgery.