Peer mentoring is an increasingly popular criminal justice intervention in custodial and community settings. Peer mentors are community members, often with lived experiences of criminal justice, who work or volunteer to help people in rehabilitative settings. Despite the growth of peer mentoring internationally, remarkably little research has been done in this field. This book offers the first in-depth analysis of peer mentoring in criminal justice. Drawing upon a rigorous ethnographic study of multiple community organisations in England, it identifies key features of criminal justice peer mentoring. Findings result from interviews with people delivering and using services and observations of practice. Peer Mentoring in Criminal Justice reveals a diverse practice, which can involve one-to-one sessions, group work or more informal leisure activities. Despite diversity, five dominant themes are uncovered. These include Identity, which is deployed to inspire change and elevate knowledge based on lived experiences; Agency, or a sense of self-direction, which emerges through dialogue between peers; Values or core conditions, including caring, listening and taking small steps; Change, which can be a terrifying and difficult struggle, yet can be mediated by mentors; and Power, which is at play within mentoring relationships and within the organisations, contexts and ideologies that surround peer mentoring. Peer mentoring offers mentors a practical opportunity to develop confidence, skills and hope for the future, whilst offering inspiration, care, empathy and practical support to others. Written in a clear and direct style this book will appeal to students and scholars in criminology, sociology, cultural studies, social theory and those interested in learning about the social effects of peer mentoring.