To promote the safety and well-being of youth who are incarcerated, the U.S. Departments of Justice and Education identified the importance of evidence-based mental health interventions. The purpose of this systematic review is to summarize and synthesize intervention research focusing on the mental health of youth who are incarcerated since the publication of Guiding Principles for Providing High-Quality Education in Juvenile Justice Secure Care Settings. ProQuest and Ebsco databases were searched to identify relevant published studies from 2015 to 2020. Eleven studies met the inclusion criteria. Studies mainly focused on cognitive-behavior interventions and included the following outcome domains: symptoms, functioning, personal growth, and multiple domains. To evaluate study quality, modified versions of Gersten et al.'s (2005) group design and Mulcahy et al.'s (2016) single-case design quality indicators were used. Of concern are the small number of studies, methodological limitations within studies, and lack of a common intervention and outcomes of focus that limit individual study conclusions and evaluation across studies. In particular, studies rarely included necessary information, such as participant mental health characteristics, interventionist training or qualifications, intervention details, and/or measures/reports of treatment integrity. For the Guiding Principles to be realized, one key issue is for government funding to target high-quality mental health interventions in juvenile correctional facilities within identified target areas. (PsycInfo Database Record (c) 2022 APA, all rights reserved).