Involving youth in developing and implementing prevention programs to reduce sexual violence (SV) has the potential to improve prevention outcomes. However, there has been little focus on youth-led SV prevention programs, and limited evaluation research to help guide efforts. The current study examined the effectiveness of Youth Voices in Prevention (Youth VIP) leadership retreats on SV victimization and perpetration, forms of violence related to SV (e.g., bullying), SV bystander behaviors and readiness, and perceptions of norms related to SV prevention. Results identified mixed findings for program impact, with variations in outcomes that can help guide future youth-led prevention program initiatives. Youth attending a large "kick-off" leadership retreat (that was less youth-led that subsequent smaller retreats) later reported more bystander behaviors, but also reported increased perpetration and victimization, compared to non-attending youth. However, youth attending smaller, more focused leadership retreats held during the school year, reported reductions in sexual harassment perpetration and improved bystander behaviors and attitudes compared to non-attending youth. Evaluation of moderator variables suggests that program impact was generally stronger for younger participants, sexual minority youth, and non-White youth (which were largely Native American youth in this sample). Findings suggest promise for youth-led prevention work but also highlight the need for testing the impact of different training structures and modalities.