The main aim of the study was to examine the influence of affective empathy and social norms on preventing behavior of cyberbystanders reinforcing cyberbullying. 219 students took part in an experiment conducted in junior high and high schools from three Polish school districts. The goal of the experiment was to check whether the students would forward or delete a humiliating picture. The results indicate a strong impact of previous experiences as a cyberperpetrator on cyberbystanders’ reinforcing behavior and a relevant effect of affective empathy activation, which decreased the frequency of cyberbullying enhancing behavior. No significant effect of gender or norm activation was found. Bystanders’ negative cyberbullying behavior was effectively reduced through norm priming only in the case of those individuals who were able to appropriately verbalize the contents of violated norms. It indicates that the regulatory role of social norms is subject to cognitive understanding of their contents.