Until the Brexit vote in 2016, Scotland’s relations with the island of Ireland (i.e. both Ireland and Northern Ireland) took place in the context of the UK and Ireland being member states of the European Union. Ireland looked to its relations, North-South and East-West, in that EU context; in the East-West case both to the UK as a whole but also to its constituent parts, notably Scotland and Wales. Scotland’s constitutional debate has inevitably played into Scottish-Irish relations, not least with the 2014 independence referendum, but the Irish government has tended to be adept and well-versed in dealing with constitutional sensitivities in its relations with the UK, including with respect to Scotland. Scotland’s constitutional debate continues: since the May 2021 elections to the Scottish parliament the Scottish government, has underlined its intention to hold an independence referendum during the new/current term of the Scottish parliament, something the UK government is currently opposed to. But that constitutional debate now takes place in the context of Brexit having happened, even though 62% of Scottish voters chose ‘remain’ in 2016. Scottish debates over the desirability and feasibility of independence in the EU frequently look both to Ireland and to its Nordic neighbours to the East, seeing similarly sized countries prospering and having influence within the EU. Equally, despite the pronounced difficulties in EU-UK relations over the Northern Ireland protocol, there has also been some tendency in Scotland to look at that protocol as giving Northern Ireland the access to the EU’s single market that the Scottish government would very much liked to have kept (and which it proposed as a compromise to the UK government during the Brexit negotiations). The UK left the EU on 31st January 2020 and left its single market and customs union on 31st December 2020. Scotland, inevitably, left with the rest of the UK. We now see a patchwork of differentiated relations across these two islands. Ireland remains an EU member state. Northern Ireland is part of the UK but is in the EU’s single market for goods and effectively in the EU customs union. England, Wales and Scotland are no longer in the EU’s single market or customs union; they face an internal border to Northern Ireland in the context of the protocol and a rather hard post-Brexit border to Ireland and the rest of the EU in the context of the Trade and Cooperation Agreement and the Withdrawal Agreement. Ireland and the UK are also participants in their joint Common Travel Area in terms of movement of people, meaning England, Wales, Scotland and Northern Ireland’s relations to Ireland are different from those to the rest of the EU where free movement has ended. In this article, we explore the implications of this patchwork and differentiated set of relationships that Brexit has super-imposed on pre-existing relations, focusing on Scotland’s relationship to Ireland, and their different relationships to the EU. We also consider how different constitutional scenarios could impact in future on these relations.