Child executive functions (cognitive flexibility, inhibitory control, working memory) are key to success in school. Cortisol, the primary stress hormone, is known to affect cognition; however, there is limited information about how child cortisol levels, parenting factors and child care context relate to executive functions in young children. The aim of this study was to examine relationships between child cortisol, parenting stress, parent coping, and daycare quality in relation to executive functions in children aged 3-5 years. We hypothesized that (1) poorer executive functioning would be related to higher child cortisol and higher parenting stress, and (2) positive daycare quality and positive parent coping style would buffer the effects of child cortisol and parenting stress on executive functions. A total of 101 children (53 girls, 48 boys, mean age 4.24 years [plus or minus] 0.74) with complete data on all measures were included. Three saliva samples to measure cortisol were collected at the child's daycare/preschool in one morning. Parents completed the Behavior Rating Inventory of Executive Function - Preschool Version (BRIEF-P), Parenting Stress Index (PSI), and Ways of Coping Questionnaire (WCQ). The Early Childhood Environment Rating Scale - Revised (ECERS-R) was used to measure the quality of daycare. It was found that children with poorer executive functioning had higher levels of salivary cortisol, and their parents reported higher parenting stress. However, parent coping style and quality of daycare did not modulate these relationships. Identifying ways to promote child executive functioning is an important direction for improving school readiness. (author abstract)