Objective: To assess associations between early childhood screen time trajectories and problematic media use scores by age 5.5. Methods: The present study is based on a prospective, community-based convenience sample of 315 parents of preschoolers, from Canada studied at the ages of 3.5 (2020), 4.5 (2021), and 5.5 (2022) during the Covid-19 pandemic. 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 5 0.9 h/day, 23%), average (mean 5 3.0 h/day, 56%), and high (mean 5 6.38 h/day, 21%) screen time trajectories. Parents reported child problematic media using the Problematic Media Use Measure . Short Form (PMUM-SF). Results: A multiple regression, adjusted for child sex, effortful control and parent education and stress revealed that compared to children in the low screen time trajectory, children in the high screen time trajectory had higher problematic media use scores at age 5.5 (ƒŔ 5 0.378, p < 0.001). In addition, children in the average screen time trajectory scored higher than children in the low screen time trajectory (ƒŔ 5 0.229, p . 0.001). Conclusion: Our findings suggest that higher screen use in early childhood is associated with an increased risk for the development of dysregulated media use, which can interfere with family functioning. As such, parents should be encouraged to follow screen time recommendations of .1 h/day for children between the ages of 2 and 5.  Kulcsszavak: screen time, screen use, problematic media use, early childhood, trajectory