This three-wave longitudinal study was set out to examine the interplay between individual characteristics (social standing in the classroom) and descriptive and injunctive classroom norms (behavior and attitudes, respectively) in explaining subsequent bullying behavior, defined as initiating, assisting, or reinforcing bullying. The target sample contained fourth- to sixth-grade students (n = 2,051) who attended the control schools in the Finnish evaluation of the KiVa antibullying program. Random slope multilevel analyses revealed that, over time, higher popularity or rejection, or lower acceptance were associated with increases in bullying behaviors, especially in classrooms with a high descriptive bullying norm. In contrast, the injunctive norm did not moderate the associations between social standing and engagement in bullying, except for children high on popularity. Theoretical and practical implications of the results are discussed.