Juvenile offenders have disproportionately high rates of psychiatric and substance use disorders relative to their nonoffending counterparts. Less is known about the impact of psychiatric and substance use disorders on repeat juvenile justice involvement among juveniles specifically referred for forensic mental health evaluations. We describe the demographic, psychiatric, and legal history background of 404 juveniles who underwent a court clinic forensic mental health evaluation, and we examine the association between these factors and detention rates of 20 percent over a 12-month post-evaluation period. After accounting for known predictors of reoffending, such as prior offense history and externalizing disorders, dual diagnosis (i.e., co-occurring psychiatric and substance use disorders) remained a salient predictor of future detention. Consistent with prior literature on juvenile offending, substance use may greatly enhance the likelihood of subsequent detention.