Outdoors-based youth development programs demonstrate the efficacy to improve indicators of personal growth and mental health in a range of disadvantaged young people. However, the most marginalized young people in society, who stand to benefit the most from such initiatives, remain underrepresented in the research. My Strengths Training for Life (MST4Life) is a positive youth development (PYD) intervention for young people experiencing homelessness that incorporates a life skills program and an outdoor adventure education (OAE) course. The current study presents a qualitative investigation of the OAE course to understand its role in promoting positive changes for participants. Reflexive thematic analysis led to the development of inductively driven themes which were conceptualized based on relevant theories (e.g., relational developmental systems) and models (e.g., 5 Cs of PYD). Findings highlight the benefits of a preceding life skills program to psychologically prepare participants to thrive in the unfamiliar setting of the outdoors and related challenges. During the course, adaptive developmental regulations supported participants’ basic psychological needs and fostered personal growth. Improvements in social competence was a common theme across participants and played a pivotal role in facilitating balanced development across the 5 Cs. In addition, experiences during the course promoted indicators of mental health and intentions to make positive lifestyle changes. Implications of these findings are discussed in relation to making outdoors-based youth development courses more accessible for marginalized young people, as well as how OAE and PYD programs can add value to the youth homeless sector.