Aims: To examine prospective and cross-sectional associations between screen time and blood pressure (BP) in preschool children. Methods: The Odense Child Cohort study started in January 2010. Children who were born in the municipality of Odense underwent a clinical examination at 3 and 5 years of age and their parents were asked to complete a questionnaire. A total of 628 children were included in the prospective analysis and 964 children were included in two cross-sectional analyses at 5 years of age. Multivariable adjusted linear and logistic regression models were computed to examine prospective and cross-sectional associations between screen time and BP with adjustment for putative confounding factors. Results: No significant prospective association was found between a 2-year change in screen time and systolic BP (0.55 BP percentile change per 1 h increase in screen time, 95% confidence interval (CI) −1.51 to 2.60) and diastolic BP (0.74 BP percentile change per 1 h increase in screen time, 95% CI −1.09 to 2.57). No significant cross-sectional association was observed between screen time (⩽1 h/day, >1–2 h/day, >2 h/day) and the prevalence of high BP at 5 years of age. Exposure to screen time before bedtime 2–5 days/week and ⩾6 days/week was significantly associated with a greater prevalence of high BP compared with screen time before bedtime 0–1 day/week (odds ratios 1.57 (95% CI 1.02–2.42) and 1.82 (95% CI 1.18–2.89), respectively. Conclusions: No prospective association was found between screen time and BP. However, a significant cross-sectional association was found between screen time before bedtime and high BP in preschool children.