The sharp increase in childhood obesity in recent years has been dramatic and continues to negatively impact children and their families. Low levels of physical activity (PA) during the preschool years is likely a contributing factor. Considering that most children in the U.S. attend some type of childcare, this is an ideal venue for implementing policies that shape children’s activity and sedentary (SED) patterns. The purpose of this dissertation was twofold. The first study compared levels of moderate-to-vigorous PA (MVPA) and SED in children attending licensed childcare centers with a PA-policy with those attending centers without a PA policy. The second study identified correlates (child-level, teacher-level, and classroom-level) of children’s MVPA and SED at childcare. Preschoolers (191), lead teachers (23), and center directors (12) from 12 licensed childcare centers (6 intervention/6 comparison) participated in the study. Children wore accelerometers during childcare for 3 days in the spring (April/May) of 2016. For the first study, separate mixed-model ANCOVAs were utilized to examine group differences in MVPA and SED, with gender entered as a covariate and classroom as a random factor. Levels of MVPA (6.74 min/h vs. 5.62 min/h, p = 0.06) and SED (29.97 min/h vs. 31.30 min/h, p = 0.32) were not significantly different between intervention and comparison groups, Findings from study one suggest the implementing a PA policy may not improving children’s PA behaviors, although compliance to policy guidelines was low. For study two, accelerometry data were utilized to examine potential correlates (measured by surveys completed by parents, teachers, and directors) of children’s PA and SED. Correlation and mixed-model regression analyses were conducted to examine associations between 18 potential correlates across multiple domains (demographic, anthropometric, social, and environmental), accounting for gender and clustering of activity within classrooms. Results from study two indicate that gender (boys) (p < .01), time spent outdoors (p < .05) and the amount of play equipment available (p < .05) were positively associated with MVPA, and gender (boys) (p < .01), and time spent outdoors (p < .05) were negatively associated with SED.