The international dimension of the agencies examined appears to be instrumental to their core mandate and embedded in the external dimension of the relevant European Union (EU) policies. The working arrangements and agreements concluded by European Aviation Safety Agency (EASA), Frontex and Europol are regarded by the EU agencies as forms of international cooperation, although of a practical and technical nature and sometimes not at the same level as a 'treaty'. The analysis of the content, wording and structure of the international cooperation instruments concluded by EASA, Frontex and Europol revealed that they can be qualified as binding instruments or, at least, as including limited substantive and procedural obligations. The objective of Europol's cooperation agreements was to enable the exchange of information in the areas of crime covered by its legal framework. The chapter explores formal international cooperation instruments enacted by EU agencies, investigation of the international cooperation legal framework and practice of EASA, Frontex and Europol.