Military-style residential programs such as Idaho Youth Challenge Academy (IDYCA) have been established to serve youth who are at-risk for dropping out or who have already dropped out of high school. This short-term longitudinal evaluative study extended prior basic and applied research conducted at the same program. This study examined psychosocial predictors and moderators of academic, behavioral, and mental health outcomes for adolescents enrolled at IDYCA. Hypotheses were informed by a review of relevant literature as well as focus groups and collaborative discussions with leadership and program staff at IDYCA. Baseline predictors included adverse childhood experiences (e.g., Bethell, Gombojav, Solloway, & Wissow, 2015) and prior justice involvement (e.g., APA, 2012; Robison et al., 2017). Risk factors included delinquent peer affiliations within the residential program (e.g., Monahan et al., 2009). Protective factors included increased support from caring adults during the residential program (e.g., Dong & Krohn, 2016). Outcomes included staff-reported behavioral infractions accrued during the residential program and overall academic performance (i.e., grade point average), as well as self-reported mental health symptoms. Findings highlighted juvenile justice involvement as a historical risk factor for poorer institutional adjustment and academic success at IDYCA. Most importantly, the adverse effects of justice contact on behavioral adjustment were attenuated for youth who developed supportive relationships with adult staff at IDYCA. In post hoc analyses, mental health symptoms experienced during IDYCA exacerbated the adverse effects of prior justice involvement on behavioral infractions. It is hoped that this research could inform the regular and repeated use of mental health screeners and sound questionnaires to identify youth who may feel less supported and/or who have developed new or worsened mental health symptoms during the residential program. These findings may also inform referral for additional behavioral interventions and mental health services, program development, and future evaluative research at comparable residential programs.