This cohort study uses data from pediatric trauma centers to assess the recovery of children's executive function after experiencing mild-to-severe traumatic brain injury. Question What is the 3-year trajectory of recovery of executive function after mild-to-severe traumatic brain injury in children? Findings In this longitudinal cohort study of 559 children with mild, moderate, or severe traumatic brain injury or orthopedic injury, patterns of recovery differed by injury severity, age at injury, and executive function assessed. Overall, growth curve models showed children's functioning worsening most sharply from baseline to 12 months; children with severe traumatic brain injury showed a secondary worsening between 24 and 36 months on some subscales. Meaning Results suggest that changes in the recovery of children's executive function over time will require repeated assessments in order to tailor interventions. Importance Executive functions are critical for school and social success. Although these functions are adversely affected by pediatric traumatic brain injury (TBI), recovery patterns are not well established. Objective To examine 3-year trajectories of selected children's executive functions after TBI. Design, Setting, and Participants This prospective cohort study was conducted from January 22, 2013, to September 30, 2015, with 3-year follow-up at the level I pediatric trauma centers Primary Children's Hospital in Salt Lake City, Utah and Children's Memorial Hermann Hospital in Houston, Texas. Study participants included children aged 2 to 15 years with TBI or orthopedic injury (OI) who were treated at the participating hospitals. Children were consecutively recruited and stratified by injury severity and age group. A total of 625 children consented and completed a baseline survey; 559 (89%) children completed at least 1 follow-up and composed the analysis cohort. It was hypothesized that recovery would differ by injury severity, age at injury, and sex. Data analyses were performed from June to October 2019. Main Outcomes and Measures Growth curve models examined the pattern of change in the Emotional Control, Inhibit, Working Memory, and Plan-Organize subscales of the Behavior Rating Inventory of Executive Function (BRIEF) or BRIEF-Preschool. For all BRIEF subscales, higher scores indicate worse symptoms, and a score of 65 or greater represents clinical impairment. Results A total of 559 children (mean [SD] age, 8.6 [4.4] years; 356 boys [64%], 328 non-Hispanic White children [59%]) were included in the study: 155 (28%) children had mild TBI, 162 (29%) had complicated mild or moderate TBI, 90 (16%) had severe TBI, and 152 (27%) had OI. Growth curve trajectories varied by BRIEF subscale and injury severity. Overall, children with TBI did not return to their preinjury baseline, with a stepwise worsening of each outcome at 36 months by TBI severity compared with OI. Among children with severe TBI, trajectories accelerated fastest, indicating increased problems, from injury to 12 months for the Emotional Control (9.0 points; 95% CI, 6.0-11.9 points), Inhibit (3.6 points; 95% CI, 1.6-5.6 points), and Working Memory (7.0 points; 95% CI, 4.1-9.9 points) subscales. Their trajectories plateaued, with a secondary acceleration before 36 months for the Emotional Control and Working Memory subscales. Children with mild TBI had worse 36-month scores on all subscales except Inhibit compared with OI. Recovery patterns were similar for boys and girls. Conclusions and Relevance In this longitudinal cohort study of children with TBI, trajectory analysis revealed that some children worsen after a recovery plateau, suggesting a need for longitudinal reassessment beyond 1 year postinjury.