Food insecurity occurs when an individual lacks the financial resources to ensure reliable access to sufficient food to meet their dietary, nutritional and social needs. Adults living with mental ill health, particularly severe mental illness, are more likely to experience food insecurity than the general adult population. Despite this, most interventions and policy reforms in recent years have been aimed at children and families, with little regard for other vulnerable groups. Initiating a conversation about access to food can be tricky and assessing for food insecurity does not happen in mental health settings. This article provides an overview of food insecurity and how it relates to mental ill health. With reference to research evidence, the reader will gain an understanding of food insecurity, how it can be assessed and how food-insecure individuals with severe mental illness can be supported. Finally, we make policy recommendations to truly address this driver of health inequality.