With Euroskeptic parties being on the rise across European Union (EU) member states, dominant parties are pressured to reconsider their positions regarding a further European integration. Yet, dominant parties’ positional reactions to Euroskeptic challenger parties are not limited to the national level but are also required at the regional level. Transferring insights regarding party competition at the national and European level to the regional level in Germany, Spain, the Netherlands, and the United Kingdom (2008-2017), we show that regional dominant parties shift towards more positive EU positions in response to electorally successful Euroskeptic challenger parties, particularly when these challenger parties emphasised EU issues to a larger extent. These findings have important implications for our understanding of party competition in European multi-level systems in the electoral arena, for the intricacies of regional party competition in Europe, and for dominant parties’ strategies when faced with Euroskeptic challengers. Forthcoming in Journal of European Integration