In the last 5 years, the European institutional architecture of banking regulation and supervision has undergone sweeping changes, brought about by a number of sequential legislative initiatives. Such a ‘Copernican revolution’ naturally calls for investigating whether and how these different layers of reforms add up to (or can be interpreted in a way that ensures) an overall consistent, efficient and effective design for banking regulation and supervision. This is particularly the case for the European Banking Authority (EBA) and the Banking Union (BU), two new institutional players which in the public debate are sometimes dubbed as overlapping or even conflicting. This paper provides a critical analysis of this interplay and its components, also with the aim to provide food for thought for further exploration, from a private as well as a public law perspective. It starts from the reasons behind the foundation of the EBA and the BU, showing how these two new institutional players in fact were created to pursue two distinct and complementary goals and operate on two separate but interconnected institutional levels. The paper then dwells on the panoply of innovative regulatory tools which the EBA can deploy in order to accomplish its mission to foster maximum harmonisation and the creation of a single set of common rules (the ‘Single Rulebook’ or SR): technical standards, guidelines and recommendations, and other ‘soft law’ instruments, such as the QA (ii) provide more certainty on the scope and possible effects of the EBA’s mediation role; and (iii) rethink the governance of the EBA, if there is to be a more balanced interplay between national and European drivers.