This article aims to analyse the new EU Treaty’s effects and implications on external relations, especially those aspects relating to the Common Foreign and Security Policy CFSP and the European Security and Defence Policy ESDP . For this purpose, it starts its analysis with examining the unified structure which has been established by unification of the Union’s external action under a single set of principles and objectives and the existence of a single international legal personality which has always been presented as a serious obstacle for EU foreing policy’s coherence. Then, it studies the amendments and developments with regard to CFSP, and it finds that the success of a more effective EU foreign policy still depends, to a great extent, on the decisions of the most influential member states in the Union. As regards to the ESDP, it questions whether the treaty can strengthen the foundation for a common defence policy examining the new and specific mechanisms which it includes. Based on its analysis, it makes it clear that it can strengthen the legal foundation, but the implementation of activities in this field inevitably relies on most influential member states’ wills like in the CFSP field. As a conclusion, it argues that the new treaty, with its contributions, should be accepted as a positive step for EU coordination and consistency in external relations, but it is not yet sufficient to accomplish a successful CFSP/ESDP