Hepatic artery pseudoaneurysms are rare complications of blunt abdominal trauma. In the past, surgical ligation was the recommended treatment; today, it is embolization. We report a case of a child involved in a motor vehicle collision who had liver lacerations with subsequent development of hepatic artery pseudoaneurysms. In this case, embolization was not performed, and the pseudoaneurysms regressed spontaneously. Spontaneous regression has been reported previously, but its true prevalence is unknown. Our report includes full sonographic and partial computed tomographic (CT) documentation of the lesions during the course of their regression. To the best of our knowledge, this is the first report in the English literature with sonographic depiction of spontaneous thrombosis of a hepatic posttraumatic pseudoaneurysm in a child.