OBJECTIVE: To examine associations between preschooler screen time trajectories and executive functions and effortful control at age 5. METHODS: Prospective, community-based convenience sample of 315 parents of preschoolers (54% male), studied at the ages of 3.5 (2020), 4.5 (2021), and 5.5 (2022). Parent-reported screen use at the ages of 3.5, 4.5, and 5.5 was used to estimate preschooler screen use trajectories. Using latent growth modeling, we identified low (mean=.9h/d, 23%), medium (mean=3.0h/d, 56%), and high (mean=6.38h/d, 21%) screen time groups. Children completed assessments of inhibitory control and cognitive flexibility at age 5.5. Both tasks are from the National Institute of Health Toolbox. Parents reported child effortful control at the age of 3.5 and 5.5 using the Children's Behavior Questionnaire, educational attainment, and parenting stress. RESULTS: Children in the average (b=-5.24) and high (b=.9.30) screen time trajectories scored significantly lower on inhibitory control than those in the low screen time group. Children in the average and high screen time groups also scored higher than children in the low screen time group on cognitive flexibility (b=-4.50) and (b=-10.12), respectively. Finally, children in the average and high screen time groups scored lower than children in the low screen time groups on effortful control (b=-.41) and (b=-.61), respectively. CONCLUSIONS: The present study shows that stability in high levels of screen use is common among preschoolers and may forecast higher risk of cognitive difficulty and lower levels of cognitive control by the time of school entry. SUMMARY: High levels of preschooler screen use were associated with lower scores on assessments of inhibitory control, cognitive flexibility, and effortful control.