Climate change will increasingly threaten humanity’s shared interests and collective security across the globe, but particularly in the least developed countries. Faced with deteriorating conditions, humans have long turned to migration—an ancient adaptive mechanism to which humans could increasingly turn in the face of a changing climate. Cumulative effects of climate change and associated migration have serious implications for stability in nations lacking sufficient financial and human resources or good governance to adequately respond to them. Although there is a need for greater understanding of the causes of migration as well as its resulting economic and political instability, a growing body of evidence already links climate change, migration, and conflict in ways that could undermine governments and stability in key regions. Mitigating and adapting to the overlapping effects of climate change, migration, and conflict demands mobilization of resources by the international community on a scale normally reserved for issues of war and peace.