Preschool teachers are uniquely positioned to impact children's physical activity levels, yet the relationship between teachers' and children's physical activity levels has not been widely investigated. The purpose of this study was to explore preschool teachers' physical activity levels, practices, and perceptions and how this relates to children's physical activity at preschool centers. This convergent mixed methods study included eight teachers and 20 children from four preschool classrooms. Accelerometers were used to measure their physical activity. Pearson correlations were used to explore the relationship between teachers' and children's physical activity levels. Direct observation was used to contextualize children's physical activity while at preschool. Teachers completed a semi-structured interview to explore their physical activity perceptions and practices. On average, teachers and children were physically active for 50.2 ± 9.3% and 29.5 ± 7.0% of their time at preschool, respectively. A significant positive correlation (p = 0.02; r = 0.98) was found between teachers' and children's percent of time at preschool per day in moderate-to-vigorous physical activity. Children mostly engaged in low-intensity activities (stationary play; light walking) during free play both indoors and outdoors and were mostly sedentary during teacher-initiated group times. All teachers stated they had a positive influence on children's physical activity. Teachers commonly reported pain or health conditions as a barrier to their physical activity. There was a positive relationship between teachers' and children's physical activity. More research is needed to confirm this relationship and to explore the impacts of high amounts of occupational physical activity on teachers' health.