Physical activity plays an important role in childhood development and is associated with positive health, social, emotional, and academic benefits. Despite this, children are often sedentary for most of their school day and fail to meet daily activity recommendations. Incorporating physical activity breaks into the classroom can achieve many positive outcomes, however has not been widely adopted. This study used the diffusion of innovation theory as a framework to examine teacher perceptions of barriers and facilitators to incorporating physical activity breaks into their elementary classrooms. Teachers perceived compatibility with teaching philosophy and observability of benefits to most students as strong facilitators. They struggled to reconcile relative advantage and trailability, primarily due to classroom management issues associated with just a few students. Lack of complexity facilitated implementation, however upper grade teachers felt a strong need to connect activity to academics which threatened complexity. The authors conclude with recommendations to increase adoption.