A 12-year-old girl with a high fever underwent echocardiography and was found to have a myxoma that arose from the atrial side of the anterior mitral valve leaflet The tumor was successfully excised. Histologic examination of the tumor showed myxoma cells and an organized thrombus with bacterial colonization. The patient was discharged from the hospital on antibiotic treatment After remaining asymptomatic for 3 weeks, she was readmitted with acute abdomen. Ultrasonography and magnetic resonance angiography detected intra-abdominal hemorrhaging and a saccular aneurysm of the abdominal aorta. The patient underwent successful emergency surgery.