Background: Wilderness therapy is one type of residential treatment that has been shown to successfully engage adolescents in mental health and substance use treatment. A growing body of wilderness therapy outcomes research supports this and wilderness therapy is being increasingly recognized as a legitimate intervention for adolescents experiencing challenges with mental health and substance use. Some evidence suggests that not all elements of wilderness therapy necessarily work the same for all clients. The question of client fit in wilderness therapy, or what works for whom, is one that has yet to receive much empirical attention in the literature. Purpose: The purpose of this study is to examine how participation in one Canadian wilderness therapy program effects two outcome variables, trait emotional intelligence and readiness to change, and how client fit moderates these relationship. Specifically, this research examines: (1) changes in clients' trait emotional intelligence from pre-to post-wilderness therapy, (2) changes in clients' readiness to change from pre-to post-wilderness therapy, and (3) if these changes differ by pre-treatment client-level variablessex, age, funding, digital interference in everyday life, or substance abuse severity. Methodology: Research was conducted with 48 participants ranging in age from 14 to 20 years. A longitudinal case study design was