Left ventricular (LV) pseudoaneurysm is rare in children. This report describes the case of a 2-year-old previously healthy girl who was diagnosed with endocarditis and underwent resection of a large mitral valve vegetation from the posterior mitral leaflet. One month after this surgery, she was diagnosed with a large LV pseudoaneurysm based on echocardiography performed during routine outpatient follow-up. Cardiac surgery was performed urgently to address the pseudoaneurysm, given its potential to rupture spontaneously. This case emphasizes the need for a close follow-up of children with endocarditis for development of pseudoaneurysms, which is a rare but potentially fatal complication of endocarditis.