Research is sparse on who targets whom in peer aggression. In this study, we investigated the harm associated with the type of relationship between aggressed and aggressor with an international sample of over 5,000 students aged 11-16, living in 12 nations. Best friends and individuals with whom the respondent had no relationship were the least likely to engage in aggression, while one-third of peer aggression could be attributed to friends (not best friends), and classmates/peers. Greater harm was experienced between best friends only when it involved relational aggression, such as spreading rumors and being left out. Harm from aggression varied by world location and number of different experiences of aggression, while gender and age differences were inconsistent. Intervention programs could take advantage of the vital role that friends play as socializing agents during adolescence that focus on the harmfulness of aggression undertaken in the guise of a joke.