Background: Limited previous research has contrasted physical activity (PA) patterns in preschool children across different hourly patterns or segments of day, or adopted similar methodologies to compare the PA behaviors of children from different countries. The purpose of this study was to examine how the PA levels and patterns differed between 3- year-olds within and between childcare and homecare days in Finland and Australia. Material/Methods: ActiGraph GT3X accelerometers were used to monitor 121 (80 Finnish, 41 Australian) children’s PA for five consecutive days. Results: No significant country differences were observed in children’s daily total PA (light-tovigorous PA [LMVPA]), except that during childcare days Finnish children spent more time in light PA compared to Australian children. During childcare attendance hours children engaged in moderate-to-vigorous PA (MVPA) for an average of 48 minutes (SD = 24) covering 54% of their daily MVPA in Finland, and for 53 minutes (SD = 34) covering 64% of their daily MVPA in Australia. Variation in children’s hour-by-hour PA was more pronounced during childcare days than homecare days. Conclusions: Despite the variations based on cultural practices, no major differences were observed in children’s daily total PA between the countries. However, these findings provide a better understanding of 3-year-olds’ PA behavior patterns and will serve as valuable evidence for the development of PA promotion in preschool children in both Finland and in Australia.