The childcare environment represents an appropriate avenue to support physical activity among preschoolers. The aim of this study was two-fold: (1) to measure the physical activity levels of a sample of preschoolers during childcare hours; and (2) to assess which attributes (e.g., space, equipment, policies) within centre-based childcare environments influenced physical activity. Thirty-one preschoolers from 5 childcare centres across London, Canada participated. Actical accelerometers were worn by participants for one day during childcare hours to assess activity levels using a 15 second epoch length. The Environment and Policy Assessment and Observation instrument was used to conduct a full-day evaluation of the childcare environment. On average, participants engaged in 1.54 min/h of moderate-to-vigorous physical activity and 17.42 min/h of total physical activity. Sedentary opportunities, portable and fixed play equipment, and staff behaviour accounted for 49.3% of the variability in moderate-to-vigorous physical activity and 14.1% of the variability in total physical activity, with sedentary opportunities, fixed play equipment, and staff behaviours displaying an inverse relationship. Results emphasize the critical role the childcare environment plays in supporting