©AANS 2019. OBJECTIVE Blunt traumatic extracranial carotid or vertebral artery injury (i.e., traumatic cerebrovascular injury [TCVI]) occurs in 1%–2% of all blunt trauma admissions, carries a 10% risk of thromboembolic ischemic stroke, and accounts for up to 9600 strokes annually in the US. Screening CT angiograms (CTAs) of patients with trauma has become ubiquitous in recent years, and patients with initially asymptomatic TCVI are commonly treated with antiplatelet agents to prevent stroke. Prophylaxis with antiplatelets is thought to be safer than anticoagulation, which carries a significant risk of hemorrhage in patients with trauma. However, the risk of hemorrhagic complications due to antiplatelets has not been assessed in this population. METHODS This is a retrospective cohort study of patients in whom a screening CTA was obtained after admission for blunt trauma at a Level 1 trauma center. Patients with CTAs indicating TCVI were treated routinely with 325 mg aspirin daily. The risk of transfusion > 24 hours after admission was compared according to CTA findings (CTA+ or CTA- for positive or negative findings, respectively) and aspirin treatment (ASA+ or ASA- for treatment or no treatment, respectively). RESULTS The mean overall transfusion amount (number of units of packed red blood cells [PRBCs]) was 0.9 ± 2.1 for CTA+/ASA+ patients (n = 196) and 0.3 ± 1.60 for CTA-/ASA- patients (n = 2290) (p < 0.0001). In adjusted models, the overall relative risk (RR) of PRBC transfusion was 1.70 (1.32–2.20) for CTA+/ASA+ patients compared with CTA-/ASA-patients. Among age groups, participants whose ages were 50–69 years had the greatest significantly elevated RR (1.71, 95% CI 1.08–2.72) for CTA+/ASA+ patients compared with CTA-/ASA- patients. CONCLUSIONS Treatment with aspirin for the prevention of stroke in patients with initially asymptomatic TCVI carries a significantly increased risk of PRBC transfusion. Future studies are needed to determine if this risk is offset by a reduced risk of ischemic stroke.