The impact of the UK‘s exit from the EU – Brexit – is likely to be felt in Northern Ireland in a unique way. The Good Friday Agreement, ending the decades-long ‘Troubles‘ era, is presaged on mutual recognition of standards and free movement of goods, people and services between Northern Ireland (as part of the UK) and Ireland. This paper explores the politics of the Brexit process in Northern Ireland, drawing insights from both EU law and UK constitutional law, arguing that there are a number of constitutional conditions that make Northern Ireland‘s status within the UK uniquely uncertain. Brexit lacks overwhelming support in Northern Ireland – NI voted decisively to Remain in the 2016 EU Referendum. An economically and politically disruptive ‘hard‘ Brexit, overseen by a Conservative government supported by the Democratic Unionist Party, could inflame nationalists and threaten the NI peace process. Moreover, more fundamentally, the very status of NI within the UK is at stake.