Readiness to change has been identified as a predictor, moderator, and mediator of treatment. Individuals may start treatment in one stage and either stay, regress, or progress across stages, but there is little research exploring these transitions within mental health treatment. The present study addressed two aims: characterize the prevalence of stage membership and transitions, and explore predictors of stage membership and transitions. A Treatment for Adolescents with Depression Study sub-sample was used and participants (n = 383) ranged in age from 12 to 17, with a primary diagnosis of Major Depressive Disorder. The 18-item self-report Stages of Change Questionnaire was administered at baseline and week 6 of treatment. A latent transition analysis determined stage membership and transitions. Most adolescents initiated treatment in precontemplation or contemplation, and hopelessness predicted stage membership and stage transitions. This study revealed that readiness to change and hopelessness are related within the first few weeks of treatment, which may have implications for depressed adolescent’s ability to benefit from care.