This thesis aims to analyse the coherence and effectiveness of the European Union (EU) foreign policy by focusing on two crucial cases that shaped the emergence of the Common Foreign and Security Policy (CFSP) of the Union: Bosnia and Herzegovina, and Kosovo. Has the EU foreign policy been coherent and effective in Bosnia and Kosovo? The concept of “coherence” has high explanatory power to analyse the relationship between the EU institutions, the EU member states, and the EU foreign policy instruments. Accordingly, this research examines the coherence of EU foreign policy instruments used in Bosnia and Kosovo by developing a new analytical concept: “perceived coherence” which focuses on the degree of receptivity amongst local agents regarding the coherence of EU policy instruments applied in their country, namely the EU accession process, the CSDP missions and mediation. After analysing the coherence of the EU foreign policy in Bosnia and Kosovo, this study focuses on the factors that come into play between coherence and effectiveness.