We report a case of a pseudoaneurysm in the sinus of Valsalva, secondary to infective endocarditis in a child with trisomy 21. The patient had a history of subaortic stenosis, bicuspid aortic valve, and ventricular septal defect. Patch closure of the ostium of the pseudoaneurysm and aortic valve replacement was performed. The patient was discharged without severe complications.