Members of conflicting groups are motivated to restore their ingroup's agency, leading to antisocial tendencies against the outgroup. The present research tested the hypothesis that affirming conflicting groups' agency would increase their members' mutual prosociality. The effectiveness of agency affirmation was demonstrated in three contexts of conflict between groups: Switzerland and the EU following the 2014 referendum (Study 1), Israelis and Palestinians (Study 2), and Israeli rightists and leftists (Study 3). Study 1 found that in a nonconflictual context Swiss participants prioritized their moral (prosocial) over agentic goals, yet in the context of conflict with the EU, they prioritized their agentic over moral goals. This “primacy-of-agency” effect, however, was eliminated once their ingroup's agency was affirmed. Studies 2 and 3 demonstrated the positive effect of agency affirmation on prosociality among Israelis referring to Palestinians and Israeli rightists and leftists referring to the adversarial political camp. This effect was mediated by group members' readiness to relinquish some power for the sake of morality. Pointing to the importance of the affirmation's specific content, Studies 2 and 3 demonstrated that morality affirmation failed to increase prosociality. As such, the present research puts forward a promising strategy to reduce hostility and promote prosociality between conflicting groups.