According to the Terms of Reference for the Article 50 TEU negotiations between the United Kingdom and the European Union (ToR), both the UK and the EU’s default approach to the negotiations is one of transparency. However, the two negotiating parties are implementing transparency in very different ways. In stark contrast to the position expounded by the UK Prime Minister, not to provide “a running commentary” on the Brexit negotiations, the EU has promised to adopt a “maximum level of transparency”. The reason behind this difference in approach stems from the fact that transparency is not intrinsically valuable, in the sense that one does not adopt an approach of transparency for transparency’s sake. Rather, it is a concept which is very much interconnected with the evolution of society. Indeed, in functioning democracies, transparency not only means disseminating information, but also appropriately withholding information. Consequently, its implementation requires a complex balance of the interests which vary according to the constitutional structure and values operating at the relevant time. The motivation behind the extent that a transparent approach is adopted is also dictated by the desire for legitimacy. The suggestion of a “democratic deficit” has long been associated with the EU and therefore it utilises transparency as a legitimating factor. The UK, however, is certainly legitimising its approach to Brexit through reference to the referendum of 23 June 2016. After offering an overview of the constitutional frameworks of the EU and the UK in relation to the concept of transparency, the following article aims to compare and contrast the main considerations which underlie the very different positions of the two negotiating parties with regard to transparency in the Brexit negotiations.