Increasingly, altercations and arrests have been traced to youths’ actions on social media. The present paper describes E-Responder, an intervention developed through a university-community partnership to address three key goals for youth at risk of legal system involvement and firearms-related violence: (1) preventing the escalation of online provocation to in-person violence; (2) supporting youth in enhancing social media self-efficacy; and (3) supporting Violence Prevention Professionals (VPPs), already working with youth, in using social media as a tool to interrupt potential violence and leverage youth’s digital citizenship. This paper describes the E-Responder mixed-methods pilot; findings suggest that E-Responder sites identified over 100 instances of risky online behavior (22% high risk) and effectively addressed 97% of these instances. Youth participants reported significantly greater social media self-efficacy over time and compared to matched-comparison youth. Focus group (n = 12) results corroborate these patterns. Implications for future intervention, research, and policy are discussed.