Young adults between 18 and 24 years of age with mental illness are significantly less likely to receive mental health services than adults in older age groups. Nationally, higher rates of depression, substance abuse, and psychiatric issues are reported in this age group. A therapeutic model referred to as young adult transition programs has emerged to better address the unique developmental challenges found in this age group. This study examined 317 critical incidents that supported or hindered young adults in a therapeutic transition program. The research design used a combination of an instrumental case study and critical incident technique (CIT). Using interviews and the Outcome Questionnaire 45.2, the study explored indepth the experiences of 17 young adults who were alumni of a young adult transition program. The research focused on critical incidents that supported or hindered the young adult in their process of growth and change while in treatment and whether meaningful change lasted beyond treatment. Its objective was to better understand the transition experience from a participant perspective and, through the findings, inform program development and evaluation for young adult transition programs. Several significant findings emerged from the data, among them the importance of interpersonal relationships, experiential education and adventure, individualized programming, and community and culture. An understanding of these findings leads to a discussion on transformational mentoring and leadership as well as relational cultural practice and how this can support leaders of transition programs in further research and program development. The limitations of the study are discussed and suggestions for future studies are offered. This