In efforts to increase the field and society's understanding of bullying, the authors investigated how various forms of attachment (mother, peer, and school) are directly and indirectly related to bullying behavior through empathy, and whether these relationships are moderated by gender. Adolescents, of grades 7 through 9, from one middle school in Seoul were surveyed. Using structural equation modeling, the study identified significant gender differences in the direct and indirect effects of attachment on bullying behavior. For male students, greater school attachment was directly related to less bullying behavior and maternal and peer attachment had indirect effects on bullying behavior, mediated by student cognitive empathy. For female students greater maternal attachment was directly related to less bullying behavior, and peer attachment had an indirect effect on bullying behavior, mediated by student affective empathy. The study provides evidence supporting increased emphasis on empathy development in bullying prevention programs.