An 8-year-old boy was admitted to the hospital with multiple abdominal and pelvic injuries following a motor vehicle accident. During hospitalization, signs of stroke developed. Evaluation discovered the cause to be emboli originating from a large left ventricular thrombus, most probably as a result of cardiac injury. Anticoagulation therapy was initiated, the cardiac mass resolved completely within 3 days, and neurologic status subsequently improved. When possible, echocardiography should be used as part of the workup of pediatric patients after multiple trauma, even without obvious signs of chest involvement.