Extensive research into wilderness therapy has not explored who benefits the most and who does not thrive in these programs. The present study examined demographic, clinical, and familial characteristics that distinguished adolescents who improve most in wilderness therapy programs from those who deteriorate. Using data collected by the National Association of Therapeutic Schools and Programs Practice Research Network, the study sample consisted of 5639 adolescents attending wilderness therapy programs which collected and contributed data to the Practice Research Network between 2017 and 2022. Measures included the Youth Outcome Questionnaire-Self Report and the McMaster Family Assessment Device, as well as demographic, familial, and clinical data collected by program staff. Using binary and univariate logistic regression, the study found individual and familial factors that predicted membership in the top 10% of adolescent participants in terms of mental health improvement from pre-to-post wilderness therapy and those factors which predicted membership in the bottom 10% in terms of poorer mental health from pre-to-post program. Considering the intensity, length, and financial resources associated with wilderness therapy program participation, these findings have important implications for wilderness therapy program staff professional development, communication of expectations to adolescents' parents/caregivers, and program admission decisions.