The question as to whether mild traumatic brain injury (mTBI) results in persisting sequelae over and above those experienced by individuals sustaining general trauma remains controversial. This prospective study aimed to document outcomes 1 week and 3 months post-injury following mTBI assessed in the emergency department (ED) of a major adult trauma center. One hundred and twenty-three patients presenting with uncomplicated mTBI and 100 matched trauma controls completed measures of post-concussive symptoms and cognitive performance (Immediate Post-Concussion Assessment and Cognitive Testing battery; ImPACT) and pre-injury health-related quality of life (SF-36) in the ED. These measures together with measures of psychiatric status (the Mini-International Neuropsychiatric Interview [MINI]) pre- and post-injury, the Hospital Anxiety and Depression Scale, Visual Analogue Scale for Pain, Functional Assessment Questionnaire, and PTSD Checklist-Specific, were re-administered at follow-up. Participants with mTBI showed significantly more severe post-concussive symptoms in the ED and at 1 week post-injury. They performed more poorly than controls on the Visual Memory subtest of the ImPACT at 1 week and 3 months post-injury. Both the mTBI and control groups recovered well physically, and most were employed 3 months post-injury. There were no significant group differences in psychiatric function. However, the group with mild TBI was more likely to report ongoing memory and concentration problems in daily activities. Further investigation of factors associated with these ongoing problems is warranted.