The ability of multilateral environmental agreements (MEAs) to keep pace with their changing circumstances is crucial for a more effective global environmental governance. Yet, we know little about how new institutional design features are taken up by MEAs, allowing them to evolve over time. Building on Kingdon’s multiple streams theory, I conceive the development of new institutional design features as the association between streams of problems, solutions, and political receptivity at critical moments. I apply this framework to two features introduced within the United Nations Convention to Combat Desertification (UNCCD) framework and find that the main design entrepreneurs were the UNCCD Secretariat and independent scientists. The article provides important insight into characteristics that can make MEAs more adaptive. Namely, treaty bodies able to generate feedback about problems, push for solutions, and provide windows of opportunity for advocates to present and revise their proposals are found critical to the development of new design features.