Although teacher-student relationship has been shown to be associated with bullying perpetration, little is known about the mediating and moderating mechanisms underlying this relationship. The present study investigated (a) the mediating effect of deviant peer affiliation in the relationship between teacher-student relationship and bullying perpetration, and (b) the moderating effect of peer pressure in the relationship between deviant peer affiliation and bullying perpetration. Our theoretical model was examined with 2407 Chinese adolescents. Participants completed questionnaires regarding teacher-student relationship, bullying, deviant peer affiliation, and peer pressure. After controlling for gender and age, teacher-student relationship was significantly negatively associated with bullying perpetration. Mediation analysis indicated that deviant peer affiliation partially mediated the relation between teacher-student relationship and bullying perpetration. Moderated mediation analysis further revealed that the relationship between deviant peer affiliation and bullying perpetration was moderated by peer pressure. Specifically, for adolescents with high peer pressure, the relationship between deviant peer affiliation and bullying perpetration became much stronger. These results can contribute to design effective interventions aimed at preventing and reducing adolescents’ bullying perpetration.