<p>For long, binding environmental treaties have provided a basis for unified state action aimed at addressing transnational environmental issues. Traditionally, these treaties were developed by officials of sovereign states, largely to the exclusion of civil society. However, the last few decades have witnessed what appears to be the gradual democratization of environmental treaty development with the increasing emergence in this process of the voice and presence of civil society. This phenomenon is strongly exemplified by the activities surrounding the development of the 2018 Regional Agreement on Access to Information, Public Participation and Justice in Environmental Matters in Latin America and the Caribbean (the ‘Escazú Agreement’) which came into force in 2021. Thus, this article engages with the theoretical underpinnings, and broadly maps the practical progress of civil society participation in environmental treaty development in general. Against this backdrop and through the experiences surrounding the Escazú Agreement, this article mainly reflects on the scope, impact, challenges and implications of the growing involvement of civil society in what was exclusively the turf of state actors.</p>