This study aimed to determine the effects of the Active Early Learning (AEL) childcare center-based physical activity intervention on early childhood executive function and expressive vocabulary via a randomized controlled trial. Three-hundred-and-fourteen preschool children (134 girls) aged 3-5 years from 15 childcare centers were randomly assigned to the intervention (8 centers; n = 170 children) or control group (7 centers, n = 144 children) in May 2019. Participants were mostly Australian (85%) and from slightly higher areas of socio-economic status than the Australian average. There was an AEL intervention effect on inhibition ([Beta] = 0.5, p = 0.033, d = 0.29) and expressive vocabulary ([Beta] = 1.97, p = 0.001, d = 0.24). Integration of the AEL physical activity intervention into the daily childcare routine was effective in enhancing children's executive function and expressive language development.