Most research on youth mentoring relationships has focused on the mentor–mentee dyad, yet caregivers play an important role in supporting these relationships. Drawing on a large, multisite sample of youth in formal mentoring programs (N = 2165), this study investigated associations between caregiver–mentor collaboration and mentoring relationship outcomes in the context of environmental and individual youth risk factors. Analysis of novel quantitative measures assessing caregivers’ experiences of the mentoring relationships revealed two factors reflecting caregivers’ collaboration with mentors (caregiver involvement and mentor backing), and three factors reflecting caregivers’ perceptions of mentor effectiveness (meeting youth needs, advocating for youth, and supporting youth behavior). Results indicated that greater caregiver involvement was associated with higher-quality and longer-lasting mentoring relationships. Few associations between risk and mentoring relationships were observed; however, indirect effects indicated that youth environmental risk was positively associated with caregiver involvement, which, in turn, was positively associated with mentoring relationship outcomes.