The present research tests the indirect effects of intergroup contact on adolescents’ bystander intervention intentions via four potential mediators: “empathy,” “cultural openness,” “in-group bias,” and “intergroup anxiety.” British adolescents (N = 855), aged 11–13 years, completed measures of intergroup (interethnic) contact and the identified indirect variables. Intended bystander behavior was measured by presenting participants with an intergroup (immigrant) name-calling scenario. Participants rated the extent to which they would behave assertively. The findings extend previous intergroup contact research by showing a significant indirect effect of intergroup contact on assertive bystander intentions via empathy, cultural openness and in-group bias (but not via intergroup anxiety). Theoretical implications and practical suggestions for future prejudice-reduction interventions are discussed.