Introduction: Regular physical activity (PA), especially aerobic exercise, may benefit cognitive function in middle-aged and older adults, but promoting regular PA in individuals with traumatic brain injury (TBI) remains a challenge. Objective: To characterize PA and perceived barriers to PA in younger (<45 years) and middle age and older (≥45 years) individuals ≥1 year after moderate-to-severe TBI. Design: Multicenter survey study. Setting: Community. Participants: Persons who met the following criteria were included in the study: (1) 18 years and older; (2) English speaking; (3) History of moderate-tosevere TBI; (4) Followed in a TBI Model Systems Center for at least 1 year; and (5) Able to complete the survey independently. Intervention: Not applicable. Main Outcome Measure(s): PA level measured by Rapid Assessment of Physical Activity questionnaire (RAPA) and self-reported barriers to PA.Results: A total of 472 participants completed the survey (response rate of 21%). More individuals in the younger group (<45 years old) met Centers for Disease Control and Prevention (CDC) recommended aerobic PA guidelines compared to the middle-aged and older group (≥ 45 years old) (62% vs 36%, p < .001). Lack of motivation, lack of time, and fatigue were the most reported barriers. Perceived barriers to PA varied by age and PA level: the middle-aged and older individuals (≥ 45 years old) were more likely to report no barriers and inactive individuals (RAPA ≤5) more likely to report lack of motivation and money, pain, and lack of resources. Conclusion: Participants ≥45 years of age were less likely to meet the CDC PA guidelines than younger individuals after moderate-to-severe TBI. Because perceived barriers to PA varied between age groups and PA levels, individualized approaches may be needed to promote PA in this population.