The Accession of the European Union (EU) to the European Convention on Human Rights (ECHR) will mark not only the beginning of a new era in terms of the protection of Fundamental Rights in Europe, but also in terms of the EU’s participation in international courts and tribunals. Up until now, the EU has never become a party to an international agreement with such a strong adjudicatory body. Therefore, it can be expected that the EU’s accession to the ECHR will have important implications for the common assumptions surrounding the relationship between the EU and adjudicatory decision making of international organisations. Furthermore, it cannot be excluded that the articulation of EU participation in the European Court of Human Rights (ECtHR) will not be replicated in other international agreements with an international court.Consequently, the examination of the mechanism envisaging the EU’s participation in ECtHR proceedings undoubtedly raises many interesting issues as regards the EU’s external representation. There are many noteworthy questions concerning the relationship between the Court of Justice of the EU (CJEU) and the ECtHR in institutional and substantive terms. This paper focuses on an institutional matter, namely, the EU’s locus standi in the ECtHR. More precisely, it examines how the draft Accession Agreement deals with the participation of the EU in the proceedings of the ECtHR; in other words, how the co-respondent mechanism organises the participation of the EU and its Member States in ECtHR proceedings. The current institutional design of the ECHR, and more specifically the way in which the ECtHR works, leads to many problems linked with the future joint participation of the EU and its Member States: the lack of legal certainty as regards the respondent and the lack of unity when pleading or issues concerning the autonomy of the EU’s legal order create problems in terms of the EU’s locus standi.