While the poor psychosocial outcomes of young people who have experienced bullying are well known, the harm associated with experiences that do not meet the bullying criteria is not well understood. The aim of this study was to examine the level of harm associated with experiences of peer aggression, as well as bullying, by directly measuring the four elements of intent, perceived harm, repetition and power imbalance that comprise the bullying criteria. The purpose of the study was to establish whether bullying was the most harmful form of peer aggression and whether other types of peer aggression that did not comprise all elements of bullying were comparably harmful. Over 6000 students (aged 11–16) from 10 countries completed a student victimization and aggression questionnaire. Data showed that pproximately 50% of participants were not intentionally harmed through peer aggression, although this varied across countries, ranging from 10% in India to 87.5% in Taiwan. In all countries, analyses identified a group that had experienced repeated peer aggression, but with no power imbalance, comparable in size to the bullied group, suggesting that bullying is just “the tip of the iceberg”. Victims of bullying selfreported the greatest experiences of harm, although victims of repeated aggression reported comparable harm. The findings show that peer aggression experiences that do not meet the bullying criteria are also rated as harmful by victims. More research is needed to fully understand negative peer interactions that include behaviors outside the scope of the bullying definition, particularly with regard to repeated peer aggression. This study suggests that researchers should consider the level of harm experienced by individuals and avoid terminology such as bullying, while policy makers should place a strong and explicit focus on encompassing a broader realm of harmful peer aggression.