Isolated right atrial rupture after nonpenetrating blunt chest trauma is rare, and very few cases have been reported in the literature. Isolated right atrial rupture is a diagnostic challenge in these patients, who are mostly victims of motor vehicle collisions. The clinical presentation is heterogeneous and can vary depending on rupture location and size. The anatomical sites mostly involved are the appendage and the free wall followed by the superior and inferior vena cava junctions. The present case study shows a fatal isolated rupture of the right atrial appendage in a victim of a motor vehicle collision. At the emergency room, a computed tomography scan revealed a severe pericardial blood effusion, and pericardiocentesis was promptly performed. Unfortunately, the patient suddenly worsened just before cardiac surgery. Autopsy findings showed a cardiac tamponade due to a linear laceration 1.8 cm in length on the right atrial appendage. No other relevant injuries were observed. A prompt diagnosis of isolated right atrial rupture can be crucial for victims of blunt chest trauma with unexplained hypotension or hemodynamic instability to improve their chances of survival. Medicolegal issues can be raised mainly related to delayed diagnosis. Once a cardiac rupture is suspected, the injury repair is essential to achieve the best outcome.