Intrapericardial rupture of the superior vena cava resulting from blunt thoracic trauma is a rare and life-threatening condition that has to be ruled out in the presence of signs of cardiac tamponade and a history of blunt thoracic trauma. We report the case of undiagnosed superior vena cava laceration caused by a high-speed road traffic accident in a 25 year-old patient revealed by cardiac tamponade. We highlight the need of urgent surgical exploration in all patients whose condition is unstable in the setting of blunt thoracic trauma regardless of imaging conclusions.