Postgraduate master's dissertation supervision is one of the least understood aspects of academic practice. Using action research, 25 master's supervisors aimed to develop a better understanding of the complexities and challenges involved in this role. Through focus groups, individual interviews and monthly workshops, they developed and piloted resources for new supervisors. The main complexities and challenges identified and articulated were: understanding the student, accepting the unpredictability of their progress, tailoring support, giving constructive feedback, and developing their personal understanding of supervision. Following the project, those involved reported increased awareness and confidence in their supervisory role and changes in their academic practice.