This Special Issue seeks to explore the potentialities of strengthening a new field of research within migration and diversity studies: Immigrant incorporation in political parties. The point of departure of all contributions is that there is what we call a “diversity gap” between political parties as public representative organisations and diversity dynamics in democratic societies. This Special Issue seeks to explore the current strategies of political parties developing first conceptual frameworks, theoretical foundations and empirical hypothesis and approaches. The case studies come from four European countries, two from the North and two from the South of Europe: Germany, Ireland, Portugal and Spain.