This chapter examines the dynamics of Europeanization of interest groups and social movements in European Union member states. European integration has influenced interest groups and social movements since the beginning of the process in the 1950s. However, transformation has been induced by other elements such as globalization or the transformation of the state. Drawing on findings from empirical studies, this chapter analyses the change in interests, strategies, and internal organizational structures of interest groups and social movements, both in the ‘old’ and ‘new’ member states. It shows that the Europeanization of interest groups and social movements is highly differentiated, according to public policy areas, group types, and national origins.