National parliaments have been increasingly involved in EU affairs including in the reforms of EU institutions which, in most countries, they must ratify. How national parliamentarians (MPs) view and react to the challenge of Brexit is therefore of the uppermost significance for the future of European integration. The objective of this article is to analyse whether national MPs (outside the UK) see Brexit as a threat or an opportunity for the EU. It hypothesises that MPs’ evaluation of Brexit depends on three sets of factors: their ideology, their general attitude toward European integration and their country’s exposure to the consequences of Brexit. The empirical analysis relies on a survey of national MPs from nine EU countries conducted in 2017–2018. It shows that their perceptions of Brexit are part of a broader set of attitudes toward European integration and that there is a cleavage between pessimist and optimist MPs.