Teachers can contribute to the reduction or increase of peer violence in school with their beliefs about peer violence. In addition to teachers’ beliefs, their empathy can play an important role in their reaction to peer violence. The aim of this study was to examine the role of the gender of both perpetrators and victims of peer violence, as well and the gender of future teachers in assessing the aggressiveness of behavior, and in assessing the likelihood of intervention in the case of peer violence. In addition, the aim was to examine the role of the degree of future teachers’ empathy and the role of assessing the degree of aggressiveness of violent behavior in predicting the likelihood of intervention in the case of peer violence. A combination of a simulation experiment and association design was used, for which vignettes were constructed with hypothetical situations of witnessing peer violence at school. The participants in the study, which was conducted online, were 256 students (201 female) of different faculties, specializing in teaching. The results show that future teachers assess behaviors in which the victim and perpetrator are female as being more aggressive than behaviors in which the victim and perpetrator are male, and that female students assess peer violence more aggressively than male students. Female students also estimated a higher probability of intervening in a case of peer violence than male students. The results of the hierarchical regression analysis showed that the assessment of the aggressiveness of violent behavior have a significant role in explaining the probability of intervention.