Background: Few preschool children meet physical activity recommendations, whereas the majority exceeds screen-time recommendations. The purpose of this study was to examine the relationship of screen-time policies and practices with children’s physical activity and sedentary time in early care and education (ECE) centers. Methods: We conducted a cross-sectional study of 104 children (3.3 – 0.5 years; 50% girls) attending 10 ECE centers in the United States. Physical activity was measured by accelerometry. Screen-time practices were measured by classroom observation and director report. Mixed linear models were used to examine the relationship of screen-time practices with children’s total physical activity (TPA) and moderate-to-vigorous physical activity (MVPA) and sedentary time, adjusting for child’s age, sex, and BMI z-score and taking into account the clustering of children within each center. Models were repeated to include director-reported active play time as a covariate. Results: More limited/supervised screen-time (by observation) was related to higher TPA ( p = 0.0003) and lower sedentary time ( p = 0.0003). More limited/supervised screen-time (by director report) was related to higher TPA ( p 0.0001) and MVPA ( p = 0.021) and lower sedentary time ( p 0.0001). Associations remained significant when active play time was included as a covariate. TPA was inversely related to computer access ( p = 0.0015) and positively related to the use of educational screen-time compared with noneducational screen-time ( p = 0.04). Conclusions: Limiting computer usage and ensuring screen-time is educational, and integrated within the curriculum may benefit children’s physical activity levels and reduce time spent sedentary. (author abstract)