Outdoor programs involving recreational physical challenges are becoming increasingly popular for training and development purposes among adults, but rigorous studies investigating their effectiveness remain scarce. A randomized controlled trial was conducted to evaluate the effects of an outdoor adventure-based program on measures of self-efficacy, resilience, risk-taking propensity, and perceived stress. Participants were randomly assigned either to an intervention condition (half-day high ropes course) or a wait-list control group. Measures were taken at baseline and four days post-intervention and on the day to measure intervention perceptions. Significant increases in self-efficacy and risk-taking propensity were observed for the intervention arm compared to the control arm. Greater intervention engagement and affective valence ratings were associated with self-efficacy change. These findings highlight the practical relevance of adventure-based experiences for organizations and educational institutions seeking to enhance young adults' self-confidence. Additionally, they emphasize the importance of tailoring interventions to individual needs and ensuring positive participant experiences to achieve desired outcomes.