Research on self-efficacy and how it is developed in K-12 educational spaces has primarily focused on traditional classroom spaces and activities. Little research has focused on self-efficacy development in the context of outdoor experiential learning. Through this study, I use focus groups, in-depth interviewing, and on-line journal prompts to explore how junior and senior high school students participating in a co-curricular leadership program describe their experiences of self-efficacy development through the program's outdoor learning experiences. Using a thematic analysis approach, I developed three core themes common to the experiences: inspiration from others, growth and transformation, and emotional resilience. Consistent with previous research on self-efficacy, participants identified performance accomplishment as the major pathway by which self-efficacy developed. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]