This paper examines brokerage dynamics in technology transfer networks (TTNs), i.e., hybrid networks of different actors operating in the transitional area between knowledge and business ecosystems (i.e., innovation ecotones), with research organizations as anchor tenants. This particular type of network is gaining increasing attention. However, despite evidence of the importance of brokerage dynamics for knowledge mobility anchored in science and technology research, three main questions remain open: Who acts as network broker in TTNs? What are their specific functions? What mechanisms do they adopt to support these functions? To answer these questions, we conducted an in-depth multi-case study focusing on three European centers of excellence in scientific research, namely the University of Cambridge (UK), the École Polytechnique Fédérale de Lausanne (Switzerland), and the Italian Institute of Technology (Italy). We find that institutional actors as well as individuals act as network brokers in TTNs, and that brokerage manifests with varying degrees of formalization related to the TTN's level of maturity. We also identify six network brokerage functions, namely conflict resolution, spreading knowledge, linking idea fragments, connecting problems to solutions, expanding the network, and strengthening the network, and five mechanisms, namely endorsement, mediation, events, antennas, and digital support systems, that support these functions.