Activists in the global South have been navigating two powerful trends since the mid-1990s: intensifying state repression and rising investment in extractive projects from the emerging economies of Brazil, Russia, India, China, and South Africa (BRICS). In this context, this article explores the underlying forces determining the formation, endurance, and power of BRICS–South transnational advocacy networks (TANs) opposed to BRICS-based corporate extraction in the global South. By analyzing activism against Chinese, Indian, and Brazilian extractive projects in Ecuador, Ethiopia, and Mozambique, respectively, the research reveals the critical importance of domestic politics and civil society characteristics in both the BRICS and host states for shaping BRICS–South TANs, including which groups assume leadership, the extent of cross-national cooperation, and the role of nonprofits headquartered in the global North. The findings uncover core reasons for the variable resiliency and capacity of BRICS–South TANs, opening up new avenues of research and offering valuable insights for activists and policymakers.