Primary objective: To examine loss to follow-up (LTFU) using a population with traumatic brain injury (TBI) to include a range of severity and to follow participants to 3 years post-injury. Also investigated were cause of TBI and employment status.Research design: The research included 947 adults from a TBI population study. Data were obtained on severity, cause of TBI and employment status and participants were followed up at 1, 3, 6, 12, 24 and 36 months after injury. Chi-squared analyses were used to examine rates of loss to follow-up.Main outcome and results: Overall LTFU increased from 22% at 1 month post-injury to 81% at 3-year follow-up. Most participants (52%) were employed at the time of their TBI, with 39% of TBIs being motor vehicle related. Lower LTFU at 2 and 3 years post-TBI was significantly associated with severe TBI. Within the mTBI sub-group significantly higher LTFU at 1 and 6 months after injury and at 2 and 3 years post-injury was associated with TBI from assault. Those sustaining mTBI from a fall or sport-related injury showed significantly lower LTFU at the 6-month, 12-month and 2-year follow-up points. The highest LTFU was noted for unemployed participants, with retired participants showing the lowest rate.