ABSTRACT: BACKGROUND:Violent injury is the leading cause of death among urban youth. Emergency department (ED) visits represent an opportunity to deliver a brief intervention (BI) to reduce violence among youth seeking medical care in high-risk communities. OBJECTIVE:The objective was to determine the efficacy of a universally applied BI addressing violence behaviors among youth presenting to an urban ED. METHODS:ED youth (14 to 20 years old) seeking medical or injury-related care in a Level I ED (October 2011-March 2015) and screening positive for a home address within the intervention or comparison neighborhood of a larger youth violence project were enrolled in this quasi-experimental study. Based on home address, participants were assigned to receive either the 30-minute therapist-delivered BI (Project Sync) or a resource brochure (enhanced usual care [EUC] condition). The Project Sync BI combined motivational interviewing and cognitive skills training, including a review of participant goals, tailored feedback, decisional balance exercises, role-playing exercises, and linkage to community resources. Participants completed validated survey measures at baseline and a 2-month follow-up assessment. Main outcome measures included self-report of physical victimization, aggression, and self-efficacy to avoid fighting. Poisson and zero-inflated Poisson regression analyses analyzed the effects of the BI, compared to the EUC condition, on primary outcomes. RESULTS:A total of 409 eligible youth (82% participation) were enrolled and assigned to receive either the BI (n = 263) or the EUC condition (n = 146). Two-month follow-up was 91% (n = 373). There were no significant baseline differences between study conditions. Among the entire sample, mean (±SD) age was 17.7 (±1.9) years, 60% were female, 93% were African American, and 79% reported receipt of public assistance. Of participants, 9% presented for a violent injury, 9% reported recent firearm carriage, 20% reported recent alcohol use, and 39% reported recent marijuana use. Compared with the EUC group, participants in the therapist BI group showed self-reported reductions in frequency of violent aggression (therapist, -46.8%; EUC, -36.9%; incident rate ratio [IRR] = 0.87; 95% confidence interval [CI] = 0.76 to 0.99) and increased self-efficacy for avoiding fighting (therapist, +7.2%; EUC, -1.3%; IRR = 1.09; 95% CI = 1.02 to 1.15). No significant changes were noted for victimization. CONCLUSIONS:Among youth seeking ED care in a high-risk community, a brief, universally applied BI shows promise in increased self-efficacy for avoiding fighting and a decrease in the frequency of violent aggression.