In the 1990s, increased inequalities and the continuous deterioration of working conditions in global value chains (GVCs), especially in labor-intensive production segments such as apparel assembly, prompted the emergence of a ‘corporate accountability movement’ made of transnational networks of non-governmental organizations (NGOs) and trade unions seeking to improve work conditions at the bottom of GVCs, by empowering workers and re-establishing the social responsibility of large profit-accumulating firms operating at the top of these global chains (Newell, 2002; Bendel, 2004; Utting, 2005a). The paper highlights key features of such networks’ modes of operation on the basis of case studies of two transnational activist campaigns in the apparel industry, respectively organized around the Matamoros factory (Mexico) in 2003 and the Hermosa manufacturing facility (El Salvador) in 2006. Three theoretical and normative ways in which these activist campaigns can be analyzed are then considered, from a market-oriented, ‘contractual’ view of governance and a seemingly milder ‘ethical’ management perspective, to an ‘institutional’ approach highlighting the role of strong counter-power, conflict and negotiation in building sustainable forms of regulation in GVCs. The significance of transnational activists campaigns is further discussed from the third, institutional perspective, highlighting the ways in which such campaigns seek to contribute, through a complex and dynamic articulation between conflict and cooperation, to the emergence of new forms of regulation more protective of workers’ rights in the global economy.