Building resilience to increasingly intense climate change impacts requires effective, urgent adaptation action at the local level. While much progress has been made within the international and national arenas, efforts to successfully implement adaptation at the subnational level remains uneven. An innovative initiative focused on building the capacity of local decision-makers and practitioners, the Local Climate Adaptive Living Facility (LoCAL) mechanism of the United Nations Capital Development Fund (UNCDF) provides performance-based climate resilience grants to local authorities in least developing and developed countries to finance adaptation interventions. To measure and strengthen LoCAL’s impact, World Resources Institute created the Assessing Climate Change Adaptation Framework (ACCAF). While designing the ACCAF, WRI identified three major challenges: incorporating good practice in adaptation monitoring and evaluation (M&E) into an existing performance-based climate resilience grant system; addressing measurement issues inherent in mainstreamed adaptation; and balancing country-specific and portfolio-wide adaptation M&E needs. This paper delves into these challenges, presents solutions and offers broader lessons that donors, practitioners and M&E specialists around the world can adopt.