Coagulopathy and older age are common and well-recognized risk factors for poorer outcomes in traumatic brain injury (TBI) patients; however, the relationships between coagulopathy and age remain unclear. We hypothesized that coagulation/fibrinolytic abnormalities are more pronounced in older patients and may be a factor in poorer outcomes. We retrospectively evaluated severe TBI cases in which fibrinogen and D-dimer were measured on arrival and 3–6 h after injury. Propensity score-matched analyses were performed to adjust baseline characteristics between older patients (the “elderly group,” aged ≥75 y) and younger patients (the “non-elderly group,” aged 16–74 y). A total of 1294 cases (elderly group: 395, non-elderly group: 899) were assessed, and propensity score matching created a matched cohort of 324 pairs. Fibrinogen on admission, the degree of reduction in fibrinogen between admission and 3–6 h post-injury, and D-dimer levels between admission and 3–6 h post-injury were significantly more abnormal in the elderly group than in the non-elderly group. On multivariate logistic regression analysis, independent risk factors for poor prognosis included low fibrinogen and high D-dimer levels on admission. Posttraumatic coagulation and fibrinolytic abnormalities are more severe in older patients, and fibrinogen and D-dimer abnormalities are negative predictive factors.