OBJECTIVES: To investigate the relationship between sleep disturbance, neurocognition, symptom severity, and recovery in children and adolescents with concussion. Sex-related comparisons were also examined. SETTING: Pediatric tertiary referral concussion clinic. PARTICIPANTS: Children and adolescents (aged 6-18 years; n = 554) diagnosed with concussion. DESIGN: Cross-sectional retrospective study. MAIN MEASURES: Assessment data were obtained from Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT) Applications. Sleep disturbance was quantified using the sleep-related domains of the Post-Concussion Symptom Scale (PCSS) and self-report sleep duration. Sleep duration was categorized as short (<7 hours), intermediate (7-9 hours), and long (>/=9 hours). Outcome measures included neurocognition, measured via composite scores of ImPACT cognitive domains (verbal memory, visual memory, visual motor speed, reaction time); symptom severity, using the PCSS; and concussion recovery time (days). RESULTS: Short sleep resulted in significantly poorer verbal memory (P = .03), visual memory (P = .02), and reaction time (P = .01). Sleep disturbance was strongly associated with total symptom burden (rho = 0.90, P < .001). Recovery time, median (interquartile range), was significantly prolonged with short sleep, 61 (30-136) days, compared with intermediate, 38 (21-72) days, and long, 34 (19-71) days, sleep (P < .001). Overall, female participants demonstrated significantly longer recovery times than male participants (mean 91 +/- 95 vs 58 +/- 85 days, P < .001). Females exhibited similar concussion recovery times irrespective of reported sleep duration (P = .95), whereas mean recovery time in males was significantly longer with short sleep (84 +/- 82 days) than with intermediate (61 +/- 106 days) and long (49 +/- 62 days) sleep (P < .001). CONCLUSION: Sleep disturbance following concussion poses as a promising modifiable risk factor to alleviate postinjury impairments, including cognitive deficits and symptom burden. Female children were found to experience more severe concussion symptoms and protracted recovery times than their male counterparts. Investigations into the factors that may contribute to sex-related differences following concussion are warranted.