This study examined how intergroup processes and social-cognitive factors shape bystander responses to bias-based and general bullying. Participants included sixth and ninth graders (N = 179, M = 13.23) who evaluated how likely they would be to intervene if they observed bullying of immigrant-origin and nonimmigrant-origin peers. Adolescents' grade, intergroup attitudes, and social-cognitive abilities were evaluated as predictors of bystander responses. Nonimmigrant-origin adolescents reported that they expect they would be less likely to intervene when the victim is an immigrant-origin peer. Furthermore, participants with more intergroup contact and higher theory of mind were more likely to expect they would intervene in response to bias-based bullying. Findings have important implications for understanding factors that inform antibullying interventions that aim to tackle bias-based bullying against immigrants.