In order to battle bullying, it can be important for students to have teachers whom they see as taking an active stand against bullying in terms of propagating antibullying norms and having an efficacious approach to decreasing bullying. This expectation was tested with data from the control schools of the Finnish evaluation of the KiVa antibullying program. Multilevel analyses of data from 2,776 fourth- to sixth-graders showed that students’ perceptions of their teachers’ efficacy in decreasing bullying was related to a lower level of peer-reported bullying. Students’ perceptions of their teachers’ efforts to decrease bullying, however, was cross-sectionally related to a higher level of peer-reported bullying, but over time was related to a reduction in peer-reported bullying. In classes where teachers were not perceived as efficacious and had to exert a great deal of effort to reduce bullying, students with probullying attitudes and without antibullying effort had the highest level of bullying. The current findings show that teachers can play an important role in antibullying programs and should be seen as targets of intervention.