Participatory research carried out by or with children, has become a well-established and valuable part of the research landscape investigating children's lives, views and needs. So too has a critical agenda about its ethical implications and methodological complexities. One criticism is that the involvement of children who may be considered ‘vulnerable’ or ‘marginalised’ has been slower to take root within mainstream participatory practice. This means that there has been less focus on how groups such as disabled children or children affected by abuse or neglect can shape and challenge adult-dominated types of knowledge and decision-making that are likely to affect them. This article reports on the findings of a qualitative systematic literature review of thirteen contemporary papers. The review was undertaken by a UK team in 2017. The included articles explored some core ethical and methodological issues involved in carrying out participatory research with vulnerable children and young people. It reports on three themes: 1) The extent to which participatory spaces could recalibrate opportunities and attention given to marginalised and silenced groups; 2) The ways in which these children and young people could develop skills and exercise political and moral agency through participatory activity, and, 3) How to facilitate meaningful engagement with individuals and groups and reconcile this with a critical appreciation of the important but limited nature of research as means of political and social change. The review provides a unique, contemporary analysis of participatory research with vulnerable children, illuminating in particular its conceptual complexities and contradictions, particularly regarding power, empowerment and voice. Its overall utility and interest is augmented by the disciplinary and geographical breadth of the included articles, rendering it relevant to many contexts and countries.