The professional resources of the juvenile justice system are often strained by the large influx of newly detained juveniles on a daily basis. Mental health professionals in these facilities face the crucial but time-consuming responsibility of rapidly identifying those with pressing clinical needs. For this purpose, the Massachusetts Youth Screening Instrument-2 (MAYSI-2; Grisso & Barnum, 2006) was developed and widely implemented as a standard component of juvenile intake processing. Building on previous research, the current study successfully replicated the MAYSI-2 factor structure with legally involved juveniles. Unlike a previous confirmatory factor analysis (Russell, Marsee, & Ryals, 2017), this sample included juveniles with extensive substance use issues. In addition, the study explored demographic differences in MAYSI-2 elevations and observed–with several notable exceptions–similar patterns across age, gender, and ethnicity. These findings support the utility of the MAYSI-2 for efficiently and effectively screening for immediate mental health needs, which helps ensure juveniles are able to benefit from interventions aimed at criminal behavior. As noted in the discussion below, however, these results also suggest a potential need to reconsider cut score guidelines for the warning (i.e., the top 10% for juvenile offenders) level of interpretation. (PsycINFO Database Record (c) 2019 APA, all rights reserved)