<p>Despite ample evidence linking self-stigma of mental illness with many negative outcomes, little is known how self-stigma may manifest during psychotherapy, especially among adolescents. In this investigation, seventy-one adolescents (ages 12–17), predominately female and White, who recently began treatment at an outpatient psychology clinic, completed surveys assessing self-stigma and symptom severity at five time points over a sixteen-week period. Multilevel modeling was utilized to assess outcomes in self-stigma. Results indicated that self-stigma did not decline over time, nor was there evidence of variable rate-of-change in our sample. Higher average psychological symptomatology was strongly associated with higher self-stigma. Additionally, when participants reported higher-than-usual symptoms, their self-stigma was also greater. Initial psychological symptomatology did not moderate rate of change in self-stigma. Findings of this study provide a novel understanding of adolescent mental illness self-stigma following the initiation of psychotherapy and highlight the need for clinicians to further consider self-stigma in treatment.</p>