The implementation of the new school reform includes 45 minutes of physical activity for all students each day. The aim of the paper is to establish the current state of evidence related to factors, which influence teachers’ perception and willingness to implement physical activity. We searched 6 databases (2000-2016) and included 24 studies. We used a socio-ecological model in presentation of the results and Rogers’ (2003) diffusion of innovations theory in the discussion of perceived facilitators and barriers. Lack of time due to academic pressure, and lack of knowledge, competence and support are some of the perceived barriers.