Counterbalancing the narrative of youth as either helpless victims or ruthless perpetrators, a new generation of research in conflict settings focuses on their peacebuilding potential, including constructs such as prosocial behaviors and civic engagement. Previous research on the impact of political violence on prosocial behaviors in mixed, finding both positive and negative links. This study examines this relation using a launch and ambient approach, which helps to disentangle these effects over time. To do so, the article prospectively examines trajectories of adolescent prosocial behaviors (N = 999; Time 1: Mage = 12.18 years, SD = 1.82, range = 10–20) over 6 consecutive years in Belfast, Northern Ireland, a setting of on-going sectarian conflict. A dual change model, which combines the strengths of auto-regressive and latent growth curves approaches, found an initial shallow decrease in prosocial behaviors that dropped more sharply in later adolescence. Exposure to sectarianism related to an accelerated decrease in prosocial behaviors. Trajectories of prosocial behaviors positively related to later social and political engagement. Intervention implications address how to promote youth prosocial behaviors and civic engagement amid protracted political conflict. This type of research is needed because participation in civic life is a good indicator of youth agency and has positive implications for society.