Two studies (N=117, 112) were conducted with school students in Northern Ireland to investigate the neglected relationship between social identity content and intergroup relations. Study 1 tested and found support for two hypotheses. The first was that the association between in-group identification and negative behavioural intentions would be moderated by antagonistic identity content. The second was that the antagonistic identity content mediates the relationship between the experience of intergroup antagonism and negative behavioural intentions. Study 2 replicated these findings at a time of reduced intergroup violence, and supplemented them with a qualitative-quantitative analysis of participants' written responses. In addition, findings demonstrate the importance of appreciating the content and meaning of social identities when theorizing about intergroup relations and developing conflict management interventions.