This article examines different forms of territorial appropriation of climate change adaptation in two French coastal areas: Aquitaine in southwest France and Martinique Island in the French West Indies. We first highlight difficulties for policy makers to govern such an issue, qualified as an unstructured or wicked problem due to its inherent transversal dimensions. We then identify key actors and processes that render this problem governable on (and by) local territories. The international and national framing process results from and contributes to an association and hybridization with other policies, especially those from coastal risk management. The comparison shows that boundary actors and organizations (a regional working group dealing with climate change and the public interest group of Aquitaine coastline) are able to facilitate territorial appropriation by mediating between different social worlds, mainly science and politics. Capacities to cross scales and boundaries in public policy making and to mobilize boundary objects are the main features of these boundary actors. However, the case studies indicate that territorial configurations of actors play a more determining role in the politicization and the making of climate change adaptation policies. Indeed, these actors are embedded in broader institutional configurations that shape the way they can perform their boundary work.