The purpose of this study was to provide 1 year follow-up data to a previous paper that compared single-session (SS) treatment to treatment-as-needed (TAN) outcomes for mild traumatic brain injury (MTBI) survivors at 3 months post-injury. Participants were 105 adults with MTBI who were recruited from consecutive admissions to two hospital emergency wards, and randomly assigned to either the SS or TAN modality. No group differences in outcome were evident at 12 months post-injury. As well, improvements seen in the groups after 3 months were maintained at 12 months. As improvements between 3 and 12 months were negligible, self-reported improvement after a treated MTBI typically occurred within the first 3 months. Brief educational intervention given soon after MTBI appears to be as helpful as more intensive treatment for most MTBI survivors for at least 12 months post-injury.