Since the launch of the Stabilization and Association Process in 1999, the European Union has become the main conflict mediator on the post-Yugoslav space. The EU’s policy towards the region of the so-called Western Balkans implies the juxtaposition of integration and conflict settlement goals, which was not the case during the previous enlargement waves. Besides promoting peacebuilding initiatives through traditional foreign policy instruments, Brussels has been practicing a complicated system of incentives and sanctions related to the European integration procedures. Progress of the post-Yugoslav republics in enlargement is conditional on their willingness to implement particular requirements. The article analyzes the efficiency of the European Union’s conditionality from the perspective of regional stability. The ambivalence of such approach lies in politicization of peacebuilding agenda as the EU advances its specific image of recent civil wars in the Balkans. Using the methods of retrospective analysis of European politics, including foreign policy documents, the author substantiates the political nature of the demands made by Brussels on the parties to the conflicts. The distinct feature of the EU enlargement policy is the hierarchization of actors in foreign policy processes, which provides various countries with different negotiating power. This conditionality, due to the value contradictions within the communities, leads to the point when the applied measures of settlement lead not to the expected normalization, but to the aggravation of the situation and polarization of the parties. Thus, the author identifies the discrepancy between the declared objectives of the European Union as a mediator and the practical results. This inconsistency has prompted the decay of neighbor relations on the post-Yugoslav space as the EU member states attempted to instrumentalize their position within the Union for the ultimate solution of bilateral disputes with candidate countries, blocking the integration process in general.