This compendium helps practitioners in humanitarian contexts select a measure for assessing the mental health and psychosocial wellbeing of children. It provides details of 48 assessment measures and approaches that have been used in different contexts and guidance to select which is relevant. For each measure it presents: an overview/description; information about with whom and for what the assessment is suitable; examples of use; restrictions in use; and where it is available from. A decision-making guide in the form of a flow chart is provided at the end of the compendium to assist the process of matching the measurement approach to context and requirements.