Despite the growing number of older adults experiencing traumatic brain injury (TBI), little information exists regarding their utilization and cost of health care services. Identifying patterns in the type of care received and determining their costs is an important first step toward understanding the return on investment and potential areas for improvement. We performed a health care utilization and cost analysis using the National Study on the Costs and Outcomes of Trauma (NSCOT) dataset. Subjects were persons 55-84 years of age with TBI treated in 69 U.S. hospitals located in 14 states (n=414, weighted n=1038). Health outcomes, health care utilization, and 1-year costs of care following TBI in 2005 U.S. dollars were estimated from hospital bills, patient surveys, medical records, and Medicare claims data. The subjects were further analyzed in three subgroups (55-64, 65-74, and 75-84 years of age). Unadjusted cost models were built, followed by a second set of models adjusting for demographic and pre-injury health status. Those in the oldest category (75-84 years) had significantly higher numbers of re-hospitalizations, home health care visits, and hours per week of unpaid care, and significantly lower numbers of physician and mental health professional visits than younger age groups (age 55-64 and 65-74 years). Significant age-related differences were seen in all health outcomes tested at 12 months post-injury except for incidence of depressive symptoms. One-year total treatment costs did not differ significantly across age categories for brain-injured older adults in either the unadjusted or adjusted models. The unadjusted total mean 1-year cost of care was $77,872 in persons aged 55-64 years, $76,903 in persons aged 65-74 years, and $72,733 in persons aged 75-84 years. There were significant differences in cost drivers among the age groups. In the unadjusted model index hospitalization costs and inpatient rehabilitation costs were significantly lower in the oldest age category, while outpatient care costs and nursing home stays were lower in the younger age categories. In the adjusted model, in addition to these cost drivers, re-hospitalization costs were significantly higher among those 75-84 years of age, and receipt of informal care from friends and family was significantly different, being lowest among those aged 65-74 years, and highest among those aged 75-84 years. Identifying variations in care that these patients are receiving and determining the costs versus benefits is an important next step in understanding potential areas for improvement.