Background: Acute traumatic coagulopathy has been described in adult trauma patients. Acute traumatic coagulopathy may be associated with higher mortality and morbidity in pediatric trauma patients. We aimed to (1) compare acute traumatic coagulopathy incidence among various age groups, using age-adjusted normal reference values for three tests of coagulation, and (2) compare acute traumatic coagulopathy–associated mortality by age. Methods: We queried our institutional trauma database for all level 1 and 2 activations with an injury severity score ≥ 9 during 2012 to 2017. Demographics, injury information, and coagulation test results were collected. Coagulopathy was defined using published age-specific and assay-specific parameters. Variables were compared among age groups (children, adults, and older adults), and logistic regression was used to determine independent associations with mortality. Results: A total of 1,983 patients were included with a median injury severity score of 17 and mortality of 12%. Prolonged partial thromboplastin time, prolonged international normalized ratio, and hypofibrinogenemia were all strongly associated with mortality among adults and children, but not among older adults (P < .001, P < .001, and P > .01, respectively). Logistic regression revealed an independent association between prolonged partial thromboplastin time and mortality (P < .001). Conclusion: Prolonged partial thromboplastin time/international normalized ratio and hypofibrinogenemia were common among trauma patients of all ages and were associated with mortality among children and adults, but not older adults, perhaps implicating age-related hemostatic biologic differences.