Purpose: This study examined changes in physical education teachers' psychosocial perspectives after participating in a yearlong professional development about Comprehensive School Physical Activity Programming. Method: Twenty-three intervention teachers attended a workshop in Year 1 and received one academic year of technical assistance and mentorship, and 30 control teachers only attended a workshop in Year 2. Both groups completed pre- and post-self-reported measures on teacher efficacy, work engagement, and affective commitment. Results: At posttest, intervention teachers reported significantly higher levels of affective commitment, and a significant positive relationship was revealed between affective commitment and the degree to which before-school physical activity was implemented. More experienced teachers (>20 years) reported significantly higher levels of the work engagement subscale of vigor at posttest. Discussion/Conclusion: Participating in a Comprehensive School Physical Activity Program professional development may positively influence teachers' job commitment levels and invigorate more experienced teachers, which may relate to Comprehensive School Physical Activity Program implementation.