NATO aspires to take the lead in understanding and adapting to the impact of climate change on security. The new Strategic Concept declares that climate change is a defining challenge of our time, with a profound impact on Allied security. Now, the Alliance and the Allies must “walk the talk” by preparing to face the emerging climate change-driven challenges and adapting their armed forces to the new climate conditions created by global warming. This paper will begin by answering the most pressing questions about NATO and climate change: Is climate change a security threat? Does climate security fit into NATO’s mission? And is NATO the best forum to address climate change? It will then review NATO’s current actions on the climate, and finally make some proposals for the Alliance to implement a climatized perspective on security to climate-proof its assets and capacities and effectively accomplish its mission and tasks.