<p>Using the Theory of Planned Behavior framework, the purpose of the present study was (1) to examine whether teachers’ perceptions of bullying seriousness, the extent to which they see bullying as a problem at school, their self-efficacy, and their antibullying training predicted their willingness to intervene and (2) to investigate whether teachers’ intervention willingness correlated with student-reported victimization rates, and whether teachers’ self-efficacy moderated this relationship. The sample included 110 seventh- and eighth-grade in-service teachers and their students (<i>n</i> = 2127) from the Midwest of the United States. Teachers read two scenarios, one on traditional bullying victimization and the other on cyberbullying victimization, and then they answered questions regarding the seriousness of bullying, whether they believed bullying was a problem at school, self-efficacy, antibullying training, and intervention willingness. Students reported how frequently they were victimized by traditional bullying and cyberbullying at two time points. Findings indicated that seriousness, problem at school, self-efficacy, and antibullying training predicted teachers’ intervention willingness in traditional bullying, while only self-efficacy and antibullying training correlated with teachers’ intervention willingness in cyberbullying. Intervention willingness was related negatively to victimization rates across 6&#xa0;months, and this relationship was moderated by self-efficacy but only for traditional bullying. More research is needed to understand the complexity of predictors and consequences of teachers’ intervention likelihood in bullying and cyberbullying.</p>