This article examines how particular understandings of trauma as a systemic form of psychosocial harm framed the establishment of the Australian Royal Commission into Institutional Responses to Child Sexual Abuse, informed its successful investigatory process, and shaped its recommendations and outcomes. In so doing, the Royal Commission makes an important contribution to the field of trauma studies, which has been characterized by contested histories and is subject to continuing debate in clinical and academic research. For much of the twentieth century, trauma and its impacts have been typically articulated through a bio-medical discourse of individual harm and health outcomes. We argue that the establishment of the Royal Commission reflected an expanded understanding of trauma, constitutive of moral, political and psychological arenas as evidenced in its methodology, conceptual approach and treatment of survivor testimony. We also argue that the institutionalization of an historically situated and politically engaged approach to trauma within the Royal Commission itself was effective in contesting narrow psychological or juridical concepts of harm by developing approaches to trauma as a system of harm with complex impacts on families, communities and indeed the nation. We evaluate the implications and consequences of this shift in the work of the Royal Commission, with particular attention to the development of an interdisciplinary relational approach to the study of trauma as a key principle in the emergence of a trauma-informed culture.