Purpose: This study aimed to: (a) compare the physical activity (PA) levels (i.e., moderate-to-vigorous PA [MVPA] and total PA [TPA]) of preschoolers in 3 different early-learning environments (center-based childcare, home-based childcare, and full-day kindergarten [FDK]); and (b) assess which characteristics (e.g., play equipment, policies, etc.) of these settings influenced preschoolers' PA. Method: Twenty-seven facilities (9 centers, 10 homes, and 8 FDK) participated in this study. Participants (aged 2.5-5 years; n = 297) were fitted with Actical[superscript TM] accelerometers for 5 consecutive days during childcare/school hours to assess their PA. The Environment and Policy Assessment and Observation (EPAO) tool was used to objectively examine the PA environment of all participating facilities. Finally, demographic questionnaires were administered to preschoolers' parents/guardians. Results: Preschoolers in FDK accumulated significantly more MVPA (p < 0.05; 3.33 min/hr) than those in center- (1.58 min/hr) and home-based (1.75 min/hr) childcare, and they accumulated significantly more TPA (p < 0.05; 20.31 min/hr) than those in center-based childcare (18.36 min/hr). For FDK, the Active Opportunities, Sedentary Opportunities, Sedentary Environment, and Fixed Play Environment subscales of the EPAO significantly impacted both MVPA and TPA. For center-based childcare, only the Sedentary Environment subscale was found to impact MVPA and TPA. No subscales influenced children's MVPA or TPA in home-based childcare. Conclusions: This research underscores the need to encourage/support preschoolers' active behaviors in early-learning settings, particularly for those in center- and home-based childcare. Furthermore, this article highlights environmental and staff characteristics on which future PA programming should focus.