The concept of epistemic communities — professional networks with authoritative and policy-relevant expertise — is well-known thanks to a 1992 special issue of International Organization. Over the past twenty years, the idea has gained some traction in International Relations scholarship, but has not evolved much beyond its original conceptualisation. Much of the research on epistemic communities has been limited to single case studies in articles, rather than broader comparative works, and has focused narrowly on groups of scientists. As a result, it is often assumed, erroneously, that epistemic communities are only comprised of scientists, and that the utility of the concept for understanding International Relations is quite narrow. Consequently, an otherwise promising approach to transnational networks has become somewhat marginalised over the years. This article revisits the concept of epistemic communities twenty years later and proposes specific innovations to the framework. In an increasingly globalising world, transnational actors are becoming progressively more numerous and influential. Epistemic communities are certainly at the forefront of these trends, and a better understanding of how they form and operate can give us a clear demonstration of how knowledge translates into power.