This chapter focuses on the comparison of three agencies operating under the Common Foreign and Security Policy (CFSP): the European Satellite Center (SatCen), the European Union Institute for Security Studies (EUISS), and the European Defense Agency (EDA). This chapter analyses their origin, structure, delegation of powers, and main activities. SatCen provides geo-information support for security decision-making, EUISS focuses on strategic analysis and CFSP support, while EDA supports Member States in developing defence capabilities. This chapter highlights the differences in their legal basis, organizational structure, and degree of independence. Key insights include the importance of these agencies in strengthening the EU’s security architecture, their role in responding to security challenges such as Russia’s invasion of Ukraine, and their contribution to European security and defence.