Little research has sought to understand programs incorporating outdoor adventure recreation and STEM, or adventure STEM. An eight-day residential outdoor camp combining adventure activities with experiential education and geology-focused informal learning opportunities was developed and delivered to adolescents. The purpose of this exploratory study was to understand the impacts of this adventure STEM camp on adolescents perceived outdoor recreation self-efficacy (ORSE). Semi-structured interviews were conducted with 15 youth participants and content analysis was used to analyze the results. Experiential education theory and self-efficacy theory informed the curriculum design, as well as the interview questions. Results indicated there was a change in ORSE beliefs and that campers had unique, yet similar, experiences. These experiences aligned with Bandura’s (1977) main sources of self-efficacy (SE) and the physiological processes through which SE beliefs are formed. Results indicated strategically adding more camp opportunities related to mastery experiences, reflection, and coping could further improve outcomes.