Fragile and conflict-affected states (FCS) already face higher temperatures than other countries and will be more exposed to extreme heat and weather events going forward. Using innovative approaches, the paper finds that in FCS, climate vulnerability and underlying fragilities—namely conflict, heavy dependence on rainfed agriculture, and weak capacity—exacerbate each other, amplifying the negative impact on people and economies. FCS suffer more severe and persistent GDP losses than other countries due to climate shocks because their underlying fragilities amplify the impact of shocks, in particular in agriculture. At the same time, climate shocks worsen underlying fragilities, namely conflict. Macro-critical adaptation policies are needed to facilitate the immediate response to climate shocks and to build climate resilience over time. Sizeable and sustained international support—especially grants, concessional financing and capacity development—is urgent to avoid worse outcomes, including forced displacement and migration. The IMF is stepping up support to FCS in dealing with climate challenges through carefully tailored policy advice, financing, and capacity development.