Objective: Mild traumatic brain injuries (mTBI) causes symptoms in the days after injury, which persist in a proportion of cases. There is debate as to the cause of these symptoms, with recent studies suggesting that post-concussional symptoms may be attributable to pain and general trauma rather than brain injury. Few studies have controlled prospectively for these factors. The present study aimed to examine outcome and its predictors in individuals with uncomplicated mTBI and trauma controls. Participants and Methods: Participants were 123 adults with uncomplicated mTBI and 100 trauma controls with minor injuries not involving the head presenting to a hospital Emergency Department (ED). Measures included the Glasgow Coma Scale and Revised Westmead PTA Scale, measures of post-concussive symptoms and cognitive performance (ImPACT), psychiatric state, health-related quality of life, pain and other life stressors. Participants were reassessed on these measures one week and three months post-injury. Results: MTBI patients reported more post-concussional symptoms than controls at acute and one-week assessments and visual memory impairment on ImPACT. By three months both groups had improved significantly, with no group differences in post-concussive symptoms, but persisting deficits in visual memory and more self-reported memory and concentration problems in mTBI participants. At one week post-injury post-concussional symptoms were predicted by presence of mTBI, being female and premorbid psychiatric history. At three months pre-injury physical or mental health problems but not mTBI were the strongest predictors of continuing symptoms, with concurrent anxiety common. Conclusions: It is important to recognize and address risk factors in managing mTBI, which appear to interact with the injury itself.