The authors report a case of Staphylococcus Aureus infectious endocarditis in a premature baby. Echocardiography on the 8th day of life showed a large vegetation on the anterior mitral leaflet without significant regurgitation. Intravenous antibiotics and platelet antiaggregant therapy were given. At three weeks of age the vegetation split into two, one part attached to the foramen ovale and the other to the anterior mitral leaflet. At one month, the development of severe mitral regurgitation led to surgical valvuloplasty in a 2 kg neonate, the vegetation on the foramen ovale having spontaneously fragmented. The ablation of the mitral vegetation associated with commissuroplasty reduced the mitral regurgitation. At 3 months after surgery, the child was asymptomatic with a minimal mitral regurgitation.