A populist surge in Europe is affecting Euro-Mediterranean cooperation 25 years after the Barcelona Process was launched, reinforcing existing trends of de-Europeanization and renationalization of foreign policies. This article analyses the landscape of political contestation of Mediterranean cooperation in Europe in a new age of populism, focusing on France, Italy and Spain as well as the Visegrad 4 states that have turned from bystanders to veto players in Mediterranean affairs. We find that the 'thick' ideologies from which populists are borrowing condition the thrust of their influence. The impact of right-wing populism trumps that of its left-wing counterpart in quantity and quality, while market-liberal populism is in decline and regional populism is mainly an issue only in Spain. Populism has personalized decision-making and shaped political agendas directly and indirectly, most notably on migration. It has whitewashed authoritarian leaders in the southern Mediterranean and fragmented the European Union's position on key issues such as the Arab–Israeli conflict. National interests and the weight of institutions have, however, formed a counterbalance to the focus on migration emanating from domestic politics. Populism alone cannot be blamed for renationalization trends that have existed before, but it does build on and reinforce them. [ABSTRACT FROM AUTHOR]