This study examined the social cognitions of outsiders and defenders about intervening in situations of victimization by bullying. Do outsiders and defenders behave differently in victimization situations because of differences in competence beliefs, or because of a selectivity effect in intervening? These issues were examined in a sample of 102 outsiders and 107 defenders who were classified into these bullying roles through a peer-nomination procedure out of a total sample of 761 10- to 14-year-old Dutch children. These children were presented with imaginary victimization events. They answered questions about their cognitions and self-efficacy beliefs about intervening in victimization situations and about handling such situations. Outsiders, compared to defenders, claimed to intervene indirectly in victimization situations rather than directly. Defenders, compared to outsiders, claimed to intervene directly in victimization situations rather than indirectly. Both outsiders and defenders claimed to be more likely to intervene when a friend was being victimized than when a neutral classmate was being victimized. Outsiders and defenders did not differ in their self-efficacy for indirect intervention, but only defenders claimed a high self-efficacy for direct intervention. Both outsiders and defenders claimed to benefit from direct help when they themselves are victimized, but only outsiders also reported to need indirect help. The results suggest that outsiders and defenders behave differently in victimization situations because of differences in competence beliefs rather than because of a selectivity effect. More generally, the results suggest that not only defenders but also outsiders have the intention to help children who are being bullied. However, outsiders' anti-bullying attempts are likely to be indirect and less firm than those of defenders. © 2013 Society for the Study of School Psychology.