Describe the epidemiology of a large cohort of older adults with isolated traumatic brain injury (TBI) and identify predictors of mortality, palliative interventions, and discharge to preinjury residence in those presenting with moderate/severe TBI. Prospective observational study of geriatric patients with TBI enrolled across 45 trauma centers. Inclusion criteria were age ≥40years, and computed tomography (CT)-verified TBI. Exclusion criteria were any other body region abbreviated injury scale score >2 and presentation at enrolling center >24hours after injury. The analysis was restricted to individuals aged ≥65 and stratified into 3 age groups: young-old (65-74), middle-old (75-84), and oldest-old (≥85). Demographic, clinical, and injury data were collected. Predictors of mortality, palliative interventions, and discharge to preinjury residence in the moderate/severe TBI group were identified using Classification and Regression Tree and Generalized Linear Mixed Models. Of the 3081 subjects enrolled in the study, 2028 were ≥65years old. Overall, 339 (16.7%) presented with a moderate/severe TBI and experienced a 64% mortality rate. A Glasgow Coma Scale (GCS) score <9 was the main predictor of mortality, CT worsening (odds ratio [OR]= 1.7, P < .04), cerebral edema (OR= 2.4, P < .04), GCS <9, and age ≥75 (OR= 2.1, P= .007) were predictors for palliative interventions, and an injury severity score ≤24 (OR= 0.087, P= .002) was associated with increased likelihood of discharge to preinjury residence in the moderate/severe TBI group. In this prospective study of a large cohort of older adults with isolated TBI, comparisons across the older age groups with moderate/severe TBI revealed that survival and favorable discharge disposition were influenced more by severity of injury rather than age itself. Indicating that chronological age alone maybe insufficient to accurately predict outcomes, and increased representation of older adults in TBI research to develop better diagnostic and prognostic tools is warranted.