The European Union as subject of international law can conclude external agreements, under a procedure which is the object of art. 218 of the Treaty on the Functioning of the European Union (TFEU). Regarding the legal force of such agreements, the Court of Justice of the European Union ruled that they were part of the EU legal order. In addition, pursuant to provisions of art. 216 para. (2) TFEU, these agreements „link Union institutions and their Member States”. However, it should be noted that the competence of the Court of Justice in Luxembourg reflects also its ability to rule, at the request of a Member State, the European Parliament, the Council or the Commission on the compatibility of an international agreement with constitutive treaties, whether prior to the entry into force of an international agreement or later. Considering this aspect, in the contents of our study, we shall highlight, by using the specialized doctrine and case law in the field, the role that the Court of Justice of EU has in the field of control over international agreements. This analysis will consider the control aimed at formal validity (compliance with the procedure of adoption), on the one hand, and the control on the substance (compliance of the agreement with EU primary law).