This book provides qualitative scholars, particularly those in self-study, with timely research and practical resources for applying critical friendship as a research tool. Drawing on over two decades of engagement as critical friends, the authors advocate for critical friendship as a means to enhance research rigor. Long valued within self-study methodology, critical friendship offers researchers opportunities for collaboration, inquiry, and reflection. Despite its widespread use, ambiguity persists about its enactment. This book addresses the need for a comprehensive resource on critical friendship application focused solely on the theoretical and methodological understanding of critical friendship. It offers clarity on tools while exploring the complexities of critical friendship. This book makes a significant contribution to the field by expanding on key topics such as trustworthiness, characteristics of critical friendship, and the selection and evaluation of critical friends. It is designed for both seasoned and novice qualitative self-study scholars, providing insight for those seeking to integrate critical friendship into their research practice.