To examine pre-existing anxiety disorders as a risk factor for increased concussion symptomology and prolonged recovery in children and adolescents.In this retrospective cohort study, we abstracted medical record data for 637 children/adolescents (5-17 years) presenting to three tertiary concussion clinics between April 2018 and March 2019. Primary outcomes were mean concussion symptom and vision symptom severity scores measured at clinic visits. Linear mixed-effects regression models were employed to investigate differences in average symptom load, vision symptom score and symptom recovery trajectories across anxiety strata, adjusted for random effects (time), age and sex. Secondary outcomes, time to concussion symptom recovery and time to return to academics and sports, respectively, were examined via log-rank tests and multivariable Cox regression.Among 637 eligible concussion patients, 155 (24%) reported pre-existing anxiety. On average, patients with anxiety reported an additional 2.64 (95% CI 1.84 to 3.44) concussion symptoms and 7.45 (95% CI 5.22 to 9.68) higher vision symptom severity scores throughout recovery versus those without, after adjusting for age and sex. There was no evidence that concussion or vision symptom trajectories varied over time between those with/without anxiety after accounting for baseline dissimilarities in symptom scores (all pinteraction >0.05). Anxiety was significantly associated with delayed symptom recovery (adjusted HR 3.34, 95% CI 2.18 to 5.12), return to school (adjusted HR 2.01, 95% CI 1.59 to 2.53) and return to physical activity (adjusted HR 1.88, 95% CI 1.49 to 2.37).Pre-existing anxiety disorders were associated with more severe symptomology and prolonged recovery after concussion in children and adolescents. These results can be referenced by providers to manage patients' recovery expectations.