Behçet's disease is a chronic multisystemic inflammatory disorder characterized by orogenital ulcerations, uveitis, and occasional cardiac involvement. This report describes an atypical presentation of pediatric Behçet's disease with pulmonary emboli and a cardiac mass. A 16-year-old boy with a 2-year history of oral ulcers presented with weight loss, fever, joint pain, and a large tumor adhering to the free wall of the heart's right ventricle. Surgical biopsy demonstrated endomyocarditis with thrombus formation and led to the diagnosis. At the 2-year follow-up evaluation, intracardiac thrombus and pulmonic emboli had not recurred. Symptom control with immunosuppressive therapy was good.