This guidance note has been triggered by an increased interest in climate change adaptation (CCA) among international development agencies, resulting in stand-alone adaptation programs as well as efforts to mainstream CCA into existing development strategies. The paper argues that Monitoring and Evaluation (M&E) will play a critical role in informing and improving adaptation polices and activities, especially given their complex nature. Twelve reasons why CCA M&E is challenging are identified as well as brief guidance on what can be done about them. Challenges include the scale, scope, and emergent nature of CCA, which cuts across normal development sectors, levels of interventions, and timeframes.