Objective:To examine associations between pre-existing anxiety symptoms, and symptoms and cognitive functioning acutely following a suspected concussion.Design:Nested case–control study.Setting:High schools in Maine, USA.Participants:Participants were identified from a dataset of 46 920 student athletes ages 13 to 18 who received baseline preseason testing. A subset of 4732 underwent testing following a suspected concussion. Of those, 517 were assessed within 72 hours after their suspected concussion and met other inclusion criteria. Nineteen injured athletes endorsed anxiety-like symptoms on the Post-Concussion Symptom Scale (PCSS) during baseline testing and were placed in the high anxiety group. Each athlete was matched to 2 injured athletes who did not endorse high levels of anxiety-like symptoms (N = 57).Main Outcome Measures:Immediate Post-Concussion Assessment and Cognitive Testing cognitive composite scores, PCSS total score, and symptom endorsement.Results:Cognitive composite scores were similar between groups across testing times (ηp2 = 0.004-0.032). The high anxiety group endorsed a greater number of symptoms than the low anxiety group (ηp2 = 0.452) and rated symptoms as more severe (ηp2 = 0.555) across testing times. Using a modified symptom score that excluded anxiety-like symptoms, a mixed analysis of variance indicated a group by injury interaction (ηp2 = 0.079); the high anxiety group reported greater increases in overall symptom severity following injury.Conclusions:Adolescent athletes who have an anxious profile at baseline are likely to experience greater symptom burden following injury. Consideration of pre-injury anxiety may inform clinical concussion management by tailoring intervention strategies (eg, incorporating mental health treatments) to facilitate concussion recovery.