Bullying has become a pervasive threat for education, health, and policy. Inadequate professional development in bullying prevention and intervention has compounded this issue. Since teachers' professional development is a critical aspect in shaping supportive, healthy, and safe learning environments as well as creating and maintaining high-quality education, the purpose of this study is to gain more insight into the motivational processes that contribute to teachers' intention to participate in future anti-bullying professional development and intervene upon encountering school bullying. The study employed self-determination theory to examine associations between K-12 teachers' (N = 414) autonomous (intrinsic and identified) and controlled (introjected and external) motivation for participating in anti-bullying training and their intention to (a) participate in future anti-bullying training and (b) intervene upon encountering school bullying. Structural equation modeling revealed that, unlike controlled motivation, teachers' autonomous motivation for participating in anti-bullying training was positively related to their intention to participate in future training and intervene upon encountering school bullying, implying that school policy and professional development should foster autonomous motivation to increase intention to intervene upon encountering school bullying. Implications for professional development, educational practice, and future research are discussed.