This study aimed to understand the process of change within Wilderness Therapy. It used grounded theory to explore development and change during the programme and relate this to theories of adolescence and engagement, particularly for adolescents in the care system. Data collected from interviews with 11 adolescents were analysed using constructionist grounded theory. The wilderness environment, the staff, and the activities were identified as interactive factors that facilitated personal development. The analysis demonstrated the influence of early engagement in overall change. Relational factors interacted with an appropriate level of support and encouragement during activities which led to the adolescents experiencing success and increases in self-worth, self-esteem and efficacy. Improvements in self-efficacy, social skills, and anger management, as well as increasingly more positive views about the world were demonstrated in all participants who completed the programme.