This article provides the first cross-national review and synthesis of available statistical and research evidence from three developed countries, the UK, Australia and the USA, and from sub-Saharan Africa, on children who provide substantial, regular or significant unpaid care to other family members ('young carers/caregivers'). It uses the issue of young carers as a window on the formulation and delivery of social policy in a global context. The article examines the extent of children's informal caregiving in each country; how young carers differ from other children; and how children's caring has been explained in research from both developed and developing countries. The article includes a review of the research, social policy and service developments for young carers in each country. National levels of awareness and policy response are characterized as 'advanced', 'intermediate', 'preliminary' or 'emerging'. Explanations are provided for variations in national policy and practice drawing on themes from the globalization literature. Global opportunities and constraints to progress, particularly in Africa, are identified. The article suggests that children's informal caring roles in both developed and developing nations can be located along a 'caregiving continuum' and that young carers, globally, have much in common irrespective of where they live or how developed are their national welfare systems. There is a need in all countries for young carers to be recognized, identified, analysed and supported as a distinct group of 'vulnerable children'.