© 2018 University of Alicante. All Rights Reserved. This paper offers an analysis of national policy approaches of Catalan socialism during the Transition until the Catalan Autonomy Statute referendum, within the framework of current reflections on nation and nationalism. The relevance of national and regional issues during the trasformation process of the political regim is reflected in its decisive role in political programmes and discourses as well as in the reconstruction of socialism in Catalonia. The aim is to raise a critical rereading of the state of the art in light of new documentary evidence and hipothesis in the field of the construction of nation building narrative by Catalan socialism. This will take into account two lines of research. First, the organizational challenges of Catalan Socialism in the unification process. Lastly, the presence of the nation and its meaning, focusing on people’s right to self-determination. This work draws on the press and the propaganda of socialist parties and their theorical-conceptual perspectives, political debates, congressional works and parliamentary sittings. The particular dimension of Catalan socialism national and regional perspective, its peculiar reconstruction through overlapping and additions, and its redefinition of Spain and Catalonia at that time spring from the controversial need to face up the Catalan issue, the acknowledgment of the Spanish State, and the opportunity to give a new regional (both sub-national and sub-state) articulation to democratic Spain.