This study examines the bystander effect in cyberbullying. On the basis of two experiments, we test whether individuals who witness cyberbullying are less willing to intervene when the number of others who have already observed the incident is increased. In addition, we inquire how differently severe cyberbullying incidents affect bystanders' intention to intervene. Our results show that a very severe cyberbullying incident boosts individuals' intention to intervene, mediated by the assessment of the situation as emergency and, in turn, by an increased feeling of responsibility. However, if there is a larger number of bystanders in a cyberbullying incident, rather than just a few, participants feel less responsible to help, and thus, they are less willing to intervene.