Transformative learning (TL) theory has rarely been used in outdoor adventure education (OAE) research despite many students describing their courses as transformative. In this study, we applied TL theory to OAE to determine whether the outcomes students reported and the activities and processes used on course produce TL. We surveyed 139 National Outdoor Leadership School (NOLS) students using the Learning Activities Survey and interviewed 20 about whether they were transformed at NOLS and if so, how they were transformed. Our findings showed that OAE can be a catalyst for TL but it depends on the student and whether they have encountered a disorienting dilemma (or challenge to their usual frames of reference). OAE courses that challenge students while offering a supportive environment and time for reflection are more likely to promote TL. Educators seeking to provide TL should focus on reflection, challenge and support in their curriculum.