ImportanceIt is unclear whether daily physical activity and sports participation relate to executive function (EF) in children.ObjectiveTo explore associations between early-life physical activity, sports participation, and executive function in primary school children.Design, Setting, and ParticipantsData for this cohort study were collected from April 2006 to December 2017 from the Groningen Expert Center for Kids with Obesity (GECKO) Drenthe birth cohort, which includes Northern Dutch children. Preschool children aged 5 to 6 years and primary school children aged 10 to 11 years with valid EF, daily physical activity, and sports participation data were included in the analysis. Data were analyzed from May 2023 to February 2024.ExposuresAt ages 5 to 6 years, daily physical activity was measured with accelerometry. At ages 10 to 11 years, sports participation data were collected using the Short Questionnaire to Assess Health–Enhancing Physical Activity.Main Outcomes and MeasuresExecutive function was assessed using the Behavior Rating Inventory of Executive Function at ages 10 to 11 years.ResultsA total of 880 children (470 female [53.4%]; mean [SD] age at EF measurement, 11.1 [0.4] years) were included. Moderate to vigorous physical activity at ages 5 to 6 years did not correlate with EF at ages 10 to 11 years (eg, Global Executive Composite [GEC]: β, 0.16; 95% CI, −0.21 to 0.53). Higher levels of light physical activity at ages 5 to 6 years were associated with poorer inhibitory control (β, 0.86; 95% CI, 0.24-1.47) and self-monitoring (β, 0.79; 95% CI, 0.09-1.48) at ages 10 to 11 years, while greater sedentary time was associated with better inhibitory control (β, −0.62; 95% CI, −1.08 to −0.16) and self-monitoring (β, −0.57; 95% CI, −1.09 to −0.06). Compared with children engaged in individual sports, team sports participants exhibited better overall EF (mean difference [SE], −3.03 [0.81]), behavior regulation (mean difference [SE], −3.39 [0.77]), and metacognition (mean difference [SE], −2.55 [0.81]). Children involved in both types of sports vs only individual sports had better EF (GEC: mean difference [SE], −2.66 [0.93]).Conclusions and RelevanceIn this cohort study of Dutch children, early-life moderate to vigorous physical activity was not associated with EF in middle childhood. Children participating in team sports at ages 10 to 11 years consistently exhibited superior EF compared with participants in individual sports.