Climate change vulnerability assessments (CCVAs) help us to understand the extent to which ecological and human systems are likely to be affected by climate change and provide information on sensitivity and exposure to changes in climate as well as the adaptive capacity of systems and populations to withstand these changes. During the three years of the U.S. Agency for International Development (USAID) African and Latin American Resilience to Climate Change (ARCC) program, specialists had an opportunity to explore and discover how best to conduct CCVAs. Their work brought improved science, methods, tools, and shared learning to the adaptation programming of USAID and its partners. The ARCC assessments—often the first of their kind in the countries in which they were completed—were distinguished by their evidence-based approach to analyses of past, present, and projected future climates. They linked changes in climate to changes in vulnerability, providing a detailed study of the dimensions of vulnerability (exposure, sensitivity, and adaptive capacity). The Compendium of Lessons Learned from ARCC Climate Change Vulnerability Assessments summarizes the lessons learned in conducting these assessments.