In the context of a deepening climate crisis, bridging the divide between pro-environmental attitudes and behavior has become increasingly important. While there is a large body of research on the relation of environmental awareness and significant life experiences (SLE), outdoor programs, and adult outdoor recreation, this thesis explores the largely unstudied potential relationship between long-distance hiking and pro-environmental behavior. This qualitative study was conducted using a grounded theory approach based on 48 interviews with long-distance Pacific Crest Trail hikers collected throughout the trail. After three cycles of coding, interviews led to the emergence of four themes, which were analyzed in the context of Hungerford and Volk’s (1990) “Model for Environmental Citizenship Behavior” to develop the hypothesis that long-distance hiking will increase long-term pro-environmental behavior within the private sphere, but not the public sphere. Forty-two hikers developed precursors to pro-environmental behavior in at least one area, with particularly significant increases in environmental sensitivity, personal investment in issues and the environment, and intention to act. Implications for environmental education include possibilities for better integrating expeditionary learning and outdoor components, which may help students develop personal environmental morals in addition to the ecological backgrounds necessary for developing environmental literacy. Further research possibilities include restructuring the methodology to minimize response bias, examining the role of adult SLE, and continuing studies on long-distance hiking.