Background: Outdoor Behavioral Healthcare (OBH) has arisen to fill a gap in mental health treatment. While research shows large positive changes in adolescent self-reports, little is known about predictors of change, longitudinal outcomes, and parent-reports of change. Objective This study sought to identify treatment outcomes up to 18 months post-discharge and predictors of change for parents of adolescent clients in OBH treatment. Methods: Parents of 659 adolescents from four OBH programs were invited to complete questionnaires at intake, discharge, and 6 and 18 months post-discharge. A regression was conducted to examine change during treatment, and a multilevel model to examine trajectories of change post-treatment. Results: OBH participants entered treatment with clinically significant levels of emotional and behavioral dysfunction, made significant change during the program, and discharged within the "normal" range of functioning. Post-discharge scores indicated that clients remained in the "normal" range of functioning 6 and 18 months post-discharge. The regression analysis found that parent intake scores and attachment disorders were predictive of in-treatment change. The MLM found that parent perceptions of treatment gains and adoption status were significant predictors of functioning post-discharge. Conclusions: Results are in-line with previous research suggesting that OBH may be helpful to adolescents experiencing a wide range of presenting problems, and adds new insights as well. Parent-reports parallel the dramatic changes in adolescent self-reports documented throughout OBH literature; data up to 18 months post-treatment shows healthy functioning per the parent perspective; and adoption and attachment appear to play a role in outcome trajectories.