This article explores the roles of transnational civil society organizations and networks in transnational social learning. It begins with an investigation into social learning within problem domains and into the ways in which such domain learning builds perspectives and capacities for effective action among domain organizations and institutions. It suggests that domain learning involves problem definition, direction setting, implementation of collective action, and performance monitoring. Transnational civil society actors appear to take five roles in domain learning: (1) identifying issues, (2) facilitating voice of marginalized stakeholders, (3) amplifying the importance of issues, (4) building bridges among diverse stakeholders, and (5) monitoring and assessing solutions. The paper then explores the circumstances in which transnational civil society actors can be expected to make special contributions in important problem domains in the future.