Our article analyzes the impact of the European Union (EU) on border conflicts, in particular how integration and association are related to conflict transformation. We approach this issue from a theoretically as well as empirically grounded constructivist perspective. On this basis we propose a stage model of conflict development, based on the degree of securitization and societal reach of conflict communication. We argue that the EU can transform border conflicts and propose a four pathway-model of EU impact. This model comprises forms of EU impact that are, on the one hand, either actor-driven or indirectly caused by the integration process and have, on the other hand, as their main target either particular policies or the wider society in border conflict areas. We then apply this model to a comparative study of border conflicts, thereby analyzing the conflicts in Northern Ireland, Greece-Turkey, Cyprus, Europe's North (EU-Russia) and Israel-Palestine. We finish with a specification of the conditions of positive and negative EU impact.