Objectives: Individual differences in long-term psychosocial functioning after concussions in children and adolescents are poorly understood. The aim of the study was to investigate potential predictors of long-term psychosocial functioning and health-related quality of life in youth after prior concussion. Methods: Participants (N=75; mean age=14.3 years old; 52% girls) with one prior concussion (n=24), multiple prior concussions (n=24), or a prior orthopedic injury and no concussion (n=27) were seen on average 2.7 years after their most recent injury. Psychosocial functioning was assessed using the self-report versions of the Behavior Assessment System for Children (BASC-2; Anxiety and Depression scales only), the Strengths and Difficulties Questionnaire, and the Pediatric Quality of Life Inventory TM 4.0. Pre-existing conditions (attention problems, learning difficulties, mood concerns, anxiety concerns, and migraines) were reported by parents using a checklist and examined as predictors of long-term functioning. Other potential predictors included age at testing, sex, time between most recent injury and testing, and number of prior concussions. Results: The groups did not differ significantly on long-term psychosocial functioning. Moreover, only pre-existing mood concerns or attention problems significantly predicted psychosocial adjustment. Conclusions: Children’s functioning before a concussion is critical to understanding outcome. Pre-injury attention and mood concerns should be assessed in clinical settings to prevent and treat long-term psychosocial problems after concussion. (JINS, 2018, 24, 540–548)