Over the past decade-and-a-half, the GEF has been a leader in supporting climate change adaptation in the developing world – by investing over US$1.3 billion to help communities, notably through the Least Developed Countries Fund (LDCF) and the Special Climate Change Fund (SCCF). The GEF has been an “early mover” in climate change adaptation. This base of past experience is not only a rich source of insights and learning, it also places the GEF in a unique position to scale-up and mainstream adaptation in the future. Monitoring and Evaluation (M&E) plays an essential role in understanding where to focus investments, what is working and what is not (and why), and learning from experience to maximize impact. Yet a number of methodological challenges remain, primarily with defining “success” in climate change adaptation (CCA) given the long-term nature of climate change and changing baseline conditions. This brief presents key STAP recommendations for strengthening CCA M&E, and for leveraging effective learning, planning, and implementation of adaptation strategies and investments in future.