Does violence beget violence among youth in a setting of protracted conflict? Framed by a developmental intergroup approach, this paper examines the mediating roles of family ethnic socialization and intergroup bias. Two time points from 466 (50% female/50% male, 51% Catholic/49% Protestant) 14- to 16-year-olds in Northern Ireland were analyzed. Bootstrapped chain mediation found that previous experience with sectarianism, or intergroup violence, was positively related to family ethnic socialization, which predicted later intergroup bias, which was related to higher levels of adolescent participation in sectarian antisocial behavior. Findings identify the importance of family processes in the link from experiencing to committing sectarian acts. Implications for preventing youth participation in sectarianism are discussed.