Intensive supervision probation (ISP) has proven generally ineffective for youth. In this article we argue that mentorship, an intervention with increasing empirical support in the literature, is a missing treatment component. We test this proposition with results from the Spotlight Serious Offender Services Unit, an urban-based Canadian ISP program that targets high-risk gang youth. Unique to Spotlight is their adoption of street mentors to work with youth in the community. Our study incorporated quantitative and qualitative approaches: client interviews and researcher observation of street mentors coupled with comparison of recidivism outcomes between a comparison group (N = 85) of high-risk young offenders and Spotlight (N = 57) clients, matched via a propensity score matching (PSM) procedure. Spotlight cases did significantly better than the comparison group on all recidivism outcomes examined. Qualitative interview and observation data supported mentorship efficacy. Given the lack of effectiveness of other ISPs observed in the literature, we argue that mentorship makes a difference.