This article shows how International Political Economy of Labour (IPEL) approaches can be fruitful in the study of working class and institutional transformation in contemporary capitalism. It draws from an analysis of variegated union strategies in the Mercedes-Benz-Vitoria Global Value Chain (MBV-GVC), located in the autonomous community of the Basque Country (north Spain). More concretely, it explains how the recurring adoption of micro-corporatist strategies at the car assembly plant undermined and fragmented working conditions whilst, in sharp contrast, the adoption of confrontational strategies in supplier companies led to the empowerment of the workforce, increasing salaries of new entrants well above new assembly workers’. This occurred parallel to Basque unions’ challenge of prevailing institutionalised forms of collective bargaining, especially by questioning the power that Provincial Metal Sector Agreements have in the regulation of salaries and working conditions of medium and small (non-unionised) companies. Thus, in exploring how Spanish and Basque trade unions’ strategies produced different institutional settings, this article argues that IPEL approaches are helpful in providing complex and nuanced accounts of the uneven development of capitalism as a result of labour’s agency.