Many adolescents are at risk for maladjustment because of adversities faced in childhood. Resiliency research has focused on the protective factors that can ameliorate those risks. Mental health professionals have used information from resiliency research to design interventions that might help at-risk children become resilient. Despite this, many programs are largely ineffective and researchers have called for more studies on the process of building resiliency. This study investigated the process by which at-risk adolescents build resiliency through an outdoor adventure program (OAP). A qualitative approach, based on grounded theory, investigated this phenomenon through in-depth interviews with at-risk adolescents who have displayed increased resiliency after participation in an OAP. This study found that Opportunity, Engagement and Longevity are three essential factors in the process of building resiliency in at-risk adolescents. Findings from this study can illuminate the unique interactive process of building resiliency through an OAP, as well as help to improve the design of intervention programs for at-risk adolescents.