Uncertainty surrounding climate change has encouraged policy makers to engage in flexible and exploratory policies and forms of policy making. The article examines the potential of experimentation in devising coastal adaptation policies, taking into account its political dimensions. We analysed a multi-level experiment, funded by the French Ministry for the Environment from 2012 to 2015, where coastal municipalities volunteered to simulate the implementation of planned retreat as an adaptation strategy. Using insights from discursive institutionalism, we tracked developments throughout the experiment period. We highlight a combined process of governance experiment, allowing social innovation at local and regional scales, and a more strategic tool for the state, governing and steering local coastal policy with new instruments. We shed light on a particular policy entrepreneur (a public organization dealing with coastal management) playing at the intersection of these two forms, and in the interplay of policy scales. Although the experiment contributed to the innovation of legal and economic instruments and produced policy feedbacks in local planning and governance, learning capacities of the multi-scale architecture are still moderate to make planned retreat a reality in the near future. The conclusion considers performative and interpretive effects of policy experiments as further research questions to explore.