Global value chains (GVCs) affect the capacity of workers to defend and to improve their working conditions. The Swiss economy is deeply integrated into GVCs, especially export sectors such as the machinery industry. The purpose of this paper is to understand how GVCs shape working conditions in this sector and what possibilities exist for workers to improve them. To address this issue, we focus on two workers' struggles in two lead firms following GVCs restructuring. Based on a class-relational approach, this paper highlights how : (1) the participation in GVCs further strengthens the labour-capital balance of power in favor of capital; (2) despite workers' determination, the mismatch of collective structures and unions' strategies largely explains their powerlessness to resist GVCs restructuring; (3) the collective action and the solidarity emerging during the conflict pave the way for individual resistance and divisions among workers respectively once the conflict ends. Finally, the paper questions current labour strategies and imagines new ones in order to contrast employers' power in GVCs.