This guide presents a basis for understanding how nutrition, specifically undernutrition, is 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 undernutrition and climate change, and provides guidance on how to: identify populations and regions vulnerable to undernutrition and the reasons for their vulnerability; establish relevant baselines that can be analysed and monitored; conduct analyses to project how undernutrition may be impacted in the future due to climate change; and identify appropriate responses to mitigate and monitor these risks over time.