This dissertation analyzes the effects of further decentralization processes, specifically the Ibarretxe Plan and the reform of the Catalan Statute, on Basque and Catalan nationalist movements in Spain. It outlines how these processes have shaped nationalist discourses and political strategies, highlighting a shift in Catalan nationalism towards considering secession, while Basque nationalism has remained relatively stable. The findings suggest that the structure of devolution processes plays a critical role in influencing nationalist movements and their constitutional preferences.