As part of the RAND Corporation's Security 2040 Initiative, the authors of this report explored a critical global challenge that will shape the security landscape over the next 20 years: contending with and preparing for the effects of climate change. Within the United States, many governmental entities, from cities to counties to military services, have already begun to prepare for and directly address climate change's impacts. The resilience of these communities and installations does not lie neatly within designated jurisdictional borders. Communities are dependent on how their neighbors, which include local military installations, choose to adapt to climate change. Likewise, military installations require the communities on which they depend for transportation, resources, and personnel to contend with and plan for climate change. Military installations and communities are coexisting and codependent entities, relying on mutual infrastructure and resources to support their respective functions. To explore this challenge, the authors reviewed and analyzed relevant literature, assessed other instances of intergovernmental collaboration, and applied the case of the Hampton Roads Sea Level Rise Preparedness and Resilience Intergovernmental Pilot Project to examine the role of collaboration in military and local government climate resilience planning. They found that collaboration between military services and local governments improves collective capacity to address climate change, and they provide insight into the attributes of effective joint planning. While limited in scope by design, the findings of this work are useful for those considering collaborative planning efforts and are intended to inspire future in-depth research on collaborative climate resilience planning.