This article analyzes the institutional strength of nationalist political parties in local political systems in Europe. For this, it establishes a first definition of nationalism as a political movement as well as an analysis of the representative functions of the parties. The paper constructs a Municipal Implementation Index that allows for the grouped measurement of the presence of nationalist organizations in Flanders, Scotland, Wales, the Basque Country, Catalonia and Galicia, taking 9 parties as a reference (New Flemish Alliance, Vlaams Belang, Scottish National Party, Plaid Cymru, Basque Nationalist Party, EH Bildu, Republican Left of Catalonia, Junts per Cat, Popular Unity Candidacies and Galician Nationalist Bloc) in order to study whether they have a relevant presence in the local governments of their respective territories by measuring their affiliation, the number of local elected officials as well as mayoralties. The article concludes that the weight of all these formations in municipal politics is quite unequal: it is a minority in Wales or Galicia and the Basque Country and Catalonia are the territories in Europe where nationalism has a more significant political force at the local level.