The purpose of this study was to understand how adolescents respond as bystanders of cyberbullying and to seek factors that might influence their actions. The study explored the effects of type of contact (online vs. face to face), form of violence (private vs. public), and empathy activation (affective and cognitive) on negative bystander behaviour understood as active participation in victimisation. The influence of experience of cyberbullying as perpetrator and as victim and gender on negative bystander behaviour was also controlled. Three experimental studies were conducted. The results indicate that online contact increases the likelihood of negative bystander behaviour. Private violence was less likely to elicit negative bystander action than was public violence. Previous experience of cyberperpetration was proved to increase the probability of negative bystander behaviour. Neither gender nor cybervictimisation affected the engagement in negative bystander behaviour in any of the studies. The inhibitory effect of empathy activation (both affective and cognitive) on negative bystander behaviour was demonstrated. Both types of cognitive empathy induction, emotion and behaviour focused, diminish the likelihood of negative bystander behaviour. The conclusions of the research are that negative bystander behaviour occurs more often in cyberspace than offline and that forms of intervention involving both affective and cognitive empathy may limit the negative bystander behaviour that supports cyberbullying. Copyright © 2012 John Wiley & Sons, Ltd.