This guide presents a basis for understanding how diarrhoeal diseases are currently influenced by climate and weather, and may be further exacerbated by climate change. It is a technical guide on how to conduct a Vulnerability & Adaptation assessment for diarrhoeal diseases and climate change, and provides guidance on how to: identify populations and regions vulnerable to diarrhoeal diseases and the reasons for their vulnerability; establish relevant baselines that can be analysed and monitored; conduct analyses to project how diarrhoeal diseases may be impacted in the future due to climate change; and identify appropriate responses to mitigate and monitor these risks over time.