<p>Transformations in the world of work have led to a weakening of power and a crisis of legitimacy for trade unions. Faced with this situation, one option open to the unions is to recover their social dimension and adopt the social movement unionism model. The objective is to analyze, using qualitative methodology, the adoption of this model by the Basque nationalist unions Euko Langileen Alkartasuna and Langile Abertzaleen Batzordeak against a background marked by political and institutional conflict over the lack of self-government and sovereignty in this territory. In fact, the membership and strike activity data for these unions indicate that the strategic revitalization process has been particularly successful. Data extraction is relied on the analysis of documents issued by the trade unions themselves and in-depth interviews with key informants. Publications on the subject as secondary sources are used to complement the analysis.</p>