Executive function (EF) is essential for academic achievement, successful work, and physical and mental health. Although evidence shows that several factors have been linked to EF, these results are mixed. This study aims to identify both biological and environmental variables associated with impaired EF in preschoolers. This study was a population-based cross-sectional study of healthy children aged 2-5 years from public and private schools in Chiang Mai, Thailand. EF was assessed using a parent report of the Behaviour Rating Inventory of Executive Function-Preschool (BRIEF-P). Multivariable logistic regression analysis was used to explore the biological and environmental factors relevant to impaired executive functioning. In a total of 1540 included children, 213 children (13.83%) were defined as impaired EF. We found that biological factors--male (odds ratio [OR], 1.41, 95% confidence interval [CI] [1.04-1.91]), overweight/obesity (OR, 1.59, 95% CI [1.10-2.31]), less physical activity (OR, 1.77, 95% CI [1.10-2.84]), and environmental factors--low maternal education (OR, 1.61, 95% CI [1.13-2.31]), permissive parenting style (OR, 2.75, 95% CI [1.24-6.13]), and excessive screen exposure (OR, 1.66, 95% CI [1.15-2.41])--are associated with an increased risk of impaired EF. Adjusting modifiable factors, such as healthy weight status, positive parenting, appropriate screen time, and adequate physical activities, may be necessary for children to promote EF.