AbstractCognitive abilities can be acutely disrupted in children and adolescents who sustain a mild traumatic brain injury (mTBI), with the potential that these disruptions may be predictive of recovery. The objective of this study was to determine if cognitive abilities in the emergency department (ED) can differentiate and predict poor symptom recovery following a pediatric mTBI. Participants included 77 male and female youth with a mTBI (mean age=13.6;SD=2.6). All participants completed computerized cognitive testing (four subtests from the CNS Vital Signs) when they presented to the ED. Symptom measurement occurred in the ED (for pre-injury), at 7–10 days, 1 month, 2 months, and 3 months post-mTBI using the post-concussion symptom inventory (PCSI). Recovery was determined using reliable change scores for symptom ratings from 28 orthopedic injury controls (mean age=13.9 years;SD=2.1). Significantly worse Reaction Time scores (i.e., rapid information processing) in the ED were found in those who remained symptomatic at 1 month. Performances on the Reaction Time and Cognitive Flexibility domain scores were predictive of symptom outcome at 1 month for youth (above and beyond sex and baseline symptom burden). Youth with low scores on Reaction Time and/or Cognitive Flexibility were nearly 15 times (95%CI=1.8–323.5) more likely to remain symptomatic at 1 month post-mTBI. No significant group differences were found at 7–10 days, 2 months, or 3 months post-injury. Rapid computerized cognitive testing in the ED following a mTBI may help clinicians predict which youth may or may not remain symptomatic at follow-up. (JINS, 2016,22, 379–387)