Background: Very few studies have properly identified how peer victimization is associated with lower achievement in middle or high school. In this context, this study examined how peer victimization at the beginning of middle school is linked with subsequent student achievement. Specifically, it assessed if the behavioral, affective, and cognitive dimensions of engagement in school play a mediation role in the relationship between peer victimization and student achievement. Methods: The sample of this study included 683 seventh graders attending 3 schools in Montreal, Canada. Students self-reported peer victimization at the beginning and end of grade 7. They also reported their levels of student engagement on the 3 dimensions (behavioral, affective, and cognitive) across 3 time points in seventh and eighth grades. Student achievement in language arts across these 2 years was also obtained through school records. Results: Peer victimization significantly predicted lower achievement over time (b = -0.24, p [less than or equal to] 0.001). Peer victimization predicted lower achievement in grade 8 indirectly through affective student engagement (b = -0.11, p < 0.05). Post hoc analyses showed that peer victimization still predicted lower achievement in grade 8 indirectly through a decrease in affective engagement (b = -0.14, p < 0.05). However, when considered alone, a decrease in cognitive engagement also acted as a mediator (b = -0.09, p < 0.05), suggesting a strong link with affective engagement. Conclusion: Our findings expose the importance to promote student engagement in school and achievement for victimized youth.