Background: To examine the relationship between attributes of early childhood education and care (ECEC) settings and children's physical activity and sedentary behavior. Methods: Cross-sectional study involving 490 children aged 2-5 years from 11 ECECs. The ECEC routine, size of the outdoor environment, and time spent in the outdoor environment were calculated for each center. Children's physical activity and sedentary time were measured using accelerometers. Multivariate linear regressions were used to examine associations of the attributes of ECEC centers with the outcome variables, adjusting for the effects of center clustering and gender. Results: Children in ECECs that offered free routines (where children can move freely between indoor and outdoor environments) had lower levels of sedentary time (28.27 min/h vs 33.15 min/h; P = .001) and spent more time in total physical activity (7.99 min/h vs 6.57 min/h; P = .008) and moderate- to vigorous-intensity physical activity (9.49 min/h vs 7.31 min/h; P = .008). Children in ECECs with an outdoor environment >400 m2 had less sedentary time (28.94 min/h vs 32.42 min/h; P = .012) than those with areas <400 m2. Conclusion: Modifiable practices such as offering a free routine and increasing time spent in outdoor environments could potentially offer an easy and sustainable way for ECEC centers to promote physical activity and reduce sedentary time among children.