National policy reform is a prerequisite for improved stewardship of the global environment and figures prominently among the goals of international environmental diplomacy and transnational advocacy campaigns. Yet research on global environmental politics has proceeded absent models of policy change in developing countries, where most of the planet's people, land, and biological diversity are found. In this article I present a theoretical framework to explain the domestic responses of developing countries to global environmental concerns. Drawing on research in Costa Rica and Bolivia, I situate the impact of global environmentalism in the context of complex, decades-long domestic struggles to create effective institutions. When international outcomes depend on protracted reforms in nations that are sovereign yet poor, policy change is driven by actors who successfully pair international resources (technical, financial, and ideational) with the domestic political resources needed to see through major policy innovations.