Objective: The present research reports a randomized controlled trial evaluating TakeCARE, a video bystander program designed to help prevent relationship and sexual violence among high school students. Method: High school students (n = 165) were randomly assigned to view TakeCARE or a control video. Students completed self-report measures of bystander behavior and bystander self-efficacy before viewing the videos. One week later, students completed the self-efficacy measure and were observed in virtual reality simulations of situations that offered opportunities to engage in bystander behavior. Measures were readministered at a 6-month follow-up. Results: Compared to students who viewed the control video, students who viewed TakeCARE self-reported more bystander behavior at the 6-month follow-up. They were also observed to engage in greater levels of bystander behavior in the virtual reality simulations at postintervention and 6-month follow-up. Self-efficacy partially mediated this effect on observed bystander behavior. Conclusion: Video bystander programs like TakeCARE might be an effective addition to high school efforts to prevent relationship and sexual violence. (PsycINFO Database Record (c) 2018 APA, all rights reserved)