This study examined the efficacy of a brief, bystander bullying intervention (STAC) among high school students using a randomized controlled design. Results indicate that intervention students reported significantly greater reductions in bullying victimization at a 30-day follow-up compared to control students. At 3 months, although the intervention group sustained initial effects, control students also reported significant reductions in victimization. Findings from this pilot study provide preliminary support for the intervention.