A case of pseudoaneurysm of the left ventricle following apparent mild blunt wall trauma presents in a 12-year-old girl. Pseudoaneurysms are external to the left ventricular wall and communicate with the left ventricular cavity by a narrow neck. The diagnosis should be entertained in children presenting with a history of chest wall trauma, systolic murmur, wide-splitting of the second heart sound, and abnormal cardiac fluoroscopy. The fatal outcome of untreated posttraumatic pseudoaneurysms indicates surgical treatment.