Introduction: The observation time in mild traumatic brain injury (mTBI) is controversial. Our aim was to assess the risk of neurological complications in mTBI with and without antithrombotic treatment., Method: We retrospectively evaluated patients with mTBI seen in the emergency room for 3 years. We considered MTBI those with Glasgow ≥13 at admission. A cranial CT was performed in all cases with ≥1 risk factor at admission and at 24 h in those with neurological impairment or initial pathological cranial CT. Complications in the following 3 months were retrospectively reviewed., Results: We evaluated 907 patients with a mean age of 73 ± 19 years. Ninety-one percent presented risk factors, with 60% on antithrombotic treatment. We detected 11% of initial brain hemorrhage, 0.4% at 24 h, and no cases at 3 months. Antithrombotic treatment was not associated with an increased risk of brain hemorrhage (9.9% with vs 11.9% without treatment, p = 0.3). 39% of the hemorrhages presented neurological symptoms (18% post-traumatic amnesia, 12% headache, 8% vomiting, 1% seizures), with 78.4% having mild symptoms. Of the 4 hemorrhages detected at 24 h, 3 were asymptomatic and one case that worsened the initial headache. No asymptomatic patient without lesion on initial clinical cranial CT presented at 24 h., Conclusions: Our study suggests that patients with asymptomatic mTBI, without a lesion on the initial cranial CT, would not require the observation period or CT control regardless of antithrombotic treatment or INR level., (Copyright © 2023 Elsevier España, S.L.U. and Sociedad Española de Medicina Interna (SEMI). All rights reserved.)