The concept of Nature-based Solutions (NbS) has increasingly been developed in the Conservation and Climate Policy arenas for the past 10 years at the international level. Pushed and developed by organizations such as the International Union for the Conservation of Nature (IUCN) in Europe, and The Nature Conservancy (TNC) in the US, this concept has also been institutionalizing in very different national and local settings. But how is this concept actually unfolding at national levels and in different policy sectors? This research, realized through a Franco-American collaboration, attempts to analyze the genealogy of the concept at the international level, its role within global climate and environmental policy, and how it has been unfolding at national and local levels in France and the US. With a specific focus on framing analysis, the paper will highlight differences and similarities on how NbS are defined, institutionalized, and implemented. The data come from semi-structured interviews realized with actors in the field of Biodiversity Conservation and Flood Policy at International and national levels, in France and the US realized between 2021 and 2024. The theoretical framework of the paper is grounded in political sociology, and tackles in particular multi-level governance analysis framework as well as environmental policy analysis.