This study sought to understand why children high in callous-unemotional (CU) traits are less responsive to targeted anti-bullying interventions. We tested the effect of CU traits on intention to stop bullying after a teacher-led anti-bullying intervention and whether this effect was explained by participants’ perceptions of the teacher’s messages. A sample of 843 students in Grade 4 and 7 (49.8% boys, Mage = 11.56) was asked to imagine having bullied a peer and being invited to a meeting with a teacher. They were then shown a video depicting what the teacher would tell them in the meeting. They were randomly assigned to three conditions with different teacher messages (bullying-condemning, empathy-raising or a combination of both) and asked to rate the extent to which they perceived the teacher had condemned the bullying, tried to raise their empathy for the victim, and blamed them as a person. Analyses conducted separately for the whole sample and a subsample of bullying perpetrators revealed that higher levels of CU traits were associated with lower intention to stop bullying and with perceiving more blaming, less bullying-condemning and less empathy-raising from the teacher. These perceptions predicted lower intention to stop and partially mediated the effects of CU traits on intention to stop in the whole sample. In the subsample of perpetrators, only the indirect effect via perceived empathy-raising was statistically significant. One reason why youth high in CU traits are more resistant to anti-bullying intervention may be their biased perceptions of the content of anti-bullying messages.