In Europe, cross-border cooperation between sub-national organizations offers many experiences, driven by organizations such as the European Union. Today, these experiences present different profiles derived from antiquity, the participating agents (local, regional, national), the level of institutionalization, the economic product or socio-economic reality, the type of interstate relations (friendly and hostile), etc. Basically, this contribution contains a case study that refers to the experience developed by Galicia and the Region of North of Portugal. The main objective is to present its historical evolution, its current institutions and the actors involved. In this way, lessons for other places and areas can be obtained.