Mild traumatic brain injury (MTBI) is common and many people recover within three months. However, a concerning number of people (up to 15%) develop chronic symptoms and disability, irrespective of injury severity. Reasons for such poor outcomes are not well understood and require further research. This mixed methods study examines factors potentially associated with outcome after MTBI to help clinicians understand why some people do not recover as expected. Quantitative (questionnaires, brain scans, cognitive tests) and qualitative (interviews) approaches will be employed to collect data for the study. The factors we are interested in include changes in brain function, and psychological factors such as coping skills, injury beliefs, personality styles, and the impact of stress. Knowledge gained from this research will help develop effective treatments targeting modifiable risk factors to improve MTBI outcomes and reduce risk for development of chronic health problems after injury.