Although the association between peer victimization and depression is well established (Hawker & Boulton, 2000; Nansel et al., 2001), little research has examined the processes whereby victimization may lead to depression. This study examined the social-cognitive processes that mediate the relationship between peer victimization and depression. A questionnaire measuring peer victimization, depression, depression rumination, self efficacy to enlist support, and collective school efficacy to stop peer aggression at two time points during one school year was completed by 1167 secondary school children. Rumination, collective school efficacy and self efficacy to enlist support from a friend partially mediated the relationship between victimization and depression. Children who were victimized ruminated more, which lead to increased levels of depression. Victims were also less likely to believe that students and teachers could work together to stop peer aggression, which impacted their propensity to access the support of friends leading to higher depression.