Costing approaches in the economic evaluation of mental health interventions are complicated by the broad societal impacts of mental health, and the multidisciplinary nature of mental health interventions. This paper aims to provide a practical guide to costing approaches across a wide range of care inputs and illness consequences relevant to the treatment of mental health. The resources needed to deliver mental health interventions are highly variable and depend on treatment settings (institutional, community), treatment providers (medical, non-medical) and formats (individual, group, electronic). Establishing the most appropriate perspective is crucial when assessing the costs associated with a particular mental health problem or when evaluating interventions to treat them. We identify five key cost categories (social care, informal care, production losses, crime and education) impacted by mental health and discuss contemporary issues in resource use measurement and valuation, including data sources and resource use instruments.