Nationalism has resurged across Europe since the 1980s, with a dramatic rise in both the number and electoral success of parties prioritising nationalism. However, nationalism has multiple forms, including ethnoregionalism and cultural protectionism, where the latter includes anti-immigration and anti-ethnic minority appeals. Parties seeking to prioritise nationalism can combine both forms in a variety of ways, and an important determinant of this combination is the EU. The EU is able to shape party appeals by influencing the ease with which parties can achieve their policy- and vote-seeking goals using that form of nationalism. However, the EU’s effect has changed over time, with EU governance reforms from the 1980s encouraging ethnoregionalism, while the EU’s response to the 2008 financial and 2015 refugee crises encouraged cultural protectionism. This paper explores the causal mechanism underpinning the EU’s influence on the saliency of different forms of nationalism by examining Italy’s Lega and Belgium’s Vlaams Belang, which together constitute a typical and most different systems design. Using qualitative process tracing focused on elite interviews triangulated with other sources of evidence, I find that the EU does encourage parties to adjust how they prioritise ethnoregionalism and cultural protectionism, as expected.