The institutional design of NJMs varies considerably in the manner they enable, empower or constrain worker and community struggles. Whereas the UNGPs effectiveness criteria, along with other key contributions to the NJM design literature, emphasise the importance of procedural fairness, across the cases we studied purely procedural efforts were insufficient to address the deep imbalances of power between business actors and aggrieved communities. However, in some cases, these imbalances were ameliorated by aspects of institutional design that the UNGPs effectiveness criteria leave implicit: the financial and human resources the NJM can mobilise, the authority it can command and the extent to which its design enhances its capacity to exercise leverage in support of human rights redress. Even where the NJM’s design provides leverage, NJM staff frequently hesitate to flex institutional muscle for fear of jeopardising crucial resources and relationships. As such, the usefulness of transnational NJMs’ interventions often depends crucially also on factors beyond institutional design, namely the extent to which aggrieved communities are able to draw on and effectively deploy other forms of leverage and influence.