Posterior clavicle dislocations are uncommon injuries but are associated with serious complications based on their proximity to mediastinal structures. In children, the physis is the weakest point structurally, making a displaced Salter I fracture more common than a true sternoclavicular joint dislocation. This injury may be missed on exam and routine radiographs unless a high suspicion is maintained. A CT scan with contrast may be helpful for diagnosis of this injury and detection of complications to mediastinal structures. Emergent reduction is required in cases where there is vascular compromise.