Object. Traumatic aneurysms occur in 10% of extracranial blunt traumatic cerebrovascular injuries (TCVI). The clinical consequences and optimal management of traumatic aneurysms are poorly understood. Methods. A prospective study of TCVI at a Level I trauma center identified 7 patients with 19 extracranial traumatic carotid artery or vertebral artery aneurysms. An additional 6 patients with 7 traumatic aneurysms were followed outside of the prospective study, giving a total of 13 patients with 26 traumatic aneurysms. All patients were treated with 325 mg aspirin daily and underwent clinical and imaging follow-up beyond the initial hospitalization. Endovascular treatment was reserved for aneurysms demonstrating significant enlargement on follow-up imaging. Clinical and radiographic features were assessed. Results. The 7 patients with traumatic aneurysms identified in the prospective cohort comprised 10.3% of all patients with TCVI. Two (15.4%) of the 13 total patients suffered an ischemic stroke in the setting of TCVI with traumatic aneurysm formation. No patient experienced an ischemic stroke or new symptoms after the initiation of antiplatelet therapy. Clinical and radiographic follow-up averaged 15.8 months (range 0.4-41.7 months) and 22.0 months (range 6.6-55.7 months), respectively. Ten (38.5%) of 26 aneurysms were not visualized on last follow-up, 10 (38.5%) were smaller, 1 (3.8%) was unchanged, and 5 (19.2%) were larger. Saccular aneurysms were more likely to enlarge than fusiform aneurysms (33.3% vs 11.8%). Results of a Fisher exact test tend to support the assertion that the 2 different aneurysm morphologies behave differently (p = 0.07). Two saccular aneurysms were treated with stenting. Conclusions. The majority of traumatic aneurysms can be managed with an antiplatelet regimen of 325 mg aspirin daily and serial imaging. Saccular aneurysms have a greater tendency to enlarge when compared with fusiform aneurysms. ©AANS, 2014.