Background: Early childhood education (ECE) centers are an important place for preschool-aged children to obtain physical activity (PA). A U.S. state government (Louisiana) recently updated requirements for licensed centers' PA and screen-time policies, which allowed for assessment of 1) ECE center practices, environment, staff behaviors, and policies changes on child-level PA and 2) state level changes on the ECE center. Methods: ECE centers were assessed at the beginning of state licensing changes and 1-year later. The ECE centers were assessed via the Environmental Policy Assessment and Observation (EPAO) tool. The EPAO Sedentary Opportunities score, which primarily assesses television viewing time, was revised to reflect viewing non-television devices (e.g. tablets). Child-level PA was measured using accelerometry. For Aim 1, mixed models assessed ECE center changes and child PA with adjustment for demographic characteristics (fixed effects), baseline EPAO score (random effects), and clustering for center. For Aim 2, paired t-tests assessed ECE center environment differences between baseline and follow-up. Results: Nine ECE centers participated and 49 preschoolers provided complete measures at both time points. For Aim 1, increases in the EPAO revised-Sedentary Opportunities score (as in less non-television screen-time) resulted in increased child PA (p = 0.02). For Aim 2, ECE centers improved their EPAO Active Opportunities and Staff Behaviors score (p = 0.04 and p = 0.02 respectively). Conclusions: ECE centers improved their environment after 1-year, resulting in additional child PA. Changes in ECE centers environment, possibly through policy, can positively influence children's PA. (author abstract)