This paper examines how overlap between trade and environmental issues are managed under the North American Free Trade Agreement, and specifically the role that the Commission for Environmental Cooperation (CEC) Secretariat plays in this process. We demonstrate how the CEC Secretariat has influenced trade–environment politics, primarily through knowledge brokering in ways that build state capacity to collaborate across borders on trade-environment issues. Specifically, we demonstrate how the Secretariat has influenced decisions related to budget allocations, cooperative activities between member states, the creation of new institutions, and evaluating allegations of parties’ failures to enforce environmental laws. Moreover, we argue that this case raises important questions concerning the appropriate role of secretariats in international politics and has important policy implications with several new secretariats currently being set up under the burgeoning number of regional trade agreements under negotiation by the United States and many others.