Previous research has extensively analyzed the role, and indicated the importance, of network management for the functioning and performance of public or governance networks. In this article, we focus on the influence of boundary spanning actors in such networks—an aspect less examined in the governance network literature. Boundary spanners are considered to be important for governance network performance. Building on the literature, we expect a mediating role of trust in this relationship. To empirically test these relationships, we conducted survey research (N = 141) among project managers involved in urban governance networks: networks around complex urban projects that include the organizations involved in the governance process (the formulation of policies, decision making, and implementation) in these complex projects. We found a strong positive relationship between the presence of boundary spanners and trust and governance network performance. The results indicate a partially mediating role of trust in this relationship. Furthermore, we found that these boundary spanners originated mainly from private and societal organizations, and less from governmental organizations.