Research has documented the presence of norm misperception in the context of school bullying, as children and adolescents typically underestimate the degree to which their peers disapprove of bullying behavior. Despite commonly held attitudes in opposition to bullies and in support of helping victims, widespread misperception of the norm makes students vulnerable to acting in a manner that reinforces bullying, as they aim to align themselves with perceived peer beliefs. This study investigated whether personalized normative feedback, a social norms intervention that juxtaposes individuals' own perceptions of peer norms against their peers' true normative values, could operate as a mechanism by which to reduce norm misperception of peer attitudes toward bullying. Whereas this type of intervention has shown promising effects in a variety of contexts, no study to date has examined its utility in the specific context of bullying. Baseline participants included 188 seventh grade students, 175 of whom were randomized into four study groups for follow-up data collection. Individuals in the experimental condition received personalized normative feedback on attitudes toward bullying. Control conditions were the following: general normative feedback on anti-bullying attitudes, the absence of normative feedback, and personalized normative feedback on a construct separate from bullying (i.e., antidrug use attitudes). Findings indicated that personalized normative feedback on bullying attitudes led to significant change in perceived peer attitudes in the direction of the group norm, with an effect size in the small-to-medium range. No intervention effects emerged on personal attitude change. Implications highlight strategies for improving the strength of similar interventions in future research as well as the positive clinical outcomes that could result from reduced norm misperception and increased engagement in prosocial bystander behavior.