Introduction: Sport-related concussions are recognized in all types of sports in athletes of all ages. While concussion presentation involves transient symptoms, some may have prolonged symptoms that linger past the typical 2-week recovery time for adults. These prolonged symptoms can affect physical, emotional, cognitive, and sleep domains. Research Significance: This thesis examined adult athletes who experience prolonged symptoms of sport-related concussion to further our understanding of the type of symptoms that are common in an understudied population. Many of the psychological and sociological deficits are not evaluated in preparation for return to sport, but the aim of the thesis is to show their need to be included. Links between psychosocial and physical impairments can drive decisions regarding return to sport. Methods: Based on the biopsychosocial model, 3 cross-sectional studies assessed which symptom domains were clinically relevant, influenced disability, and related to each other. The studies included several clinical outcome measures delivered in online format such as the concussion symptoms, fear avoidance, sleep changes, cogniphobia, pain catastrophizing, and disability post-concussion. The last study included a small sample of participants doing a qualitative interview to confirm objective findings. They were asked to reflect on mental health, sociological impacts, and physical symptoms. Results: The concussion groups showed clinically relevant levels of concussion symptoms, mental health distress, and fear avoidance behaviour. The athletes also presented with significant changes in their abilities of daily activities. Episodic memory was also found to be a deficit for this study. Athlete interviews had statements about fear, loss of self, acceptance, and emotional regulation. Limitations included changing to online formats due to Covid-19, small sample sizes, and utilization of new outcome measures. Future work would expand on the emotional and sociological findings and address cognitive tasks for adults with prolonged symptoms. Evaluation in conjunction with physical activity or training helps an athlete return to sport. Conclusions: Adult athletes with prolonged symptoms of sport-related concussion live with many physical, emotional, and sociological impairments. It is a population that needs further research to focus on their impact and future intervention plans.