Although school-based programs are effective at decreasing bullying, the majority of studies have been conducted with elementary and middle school students. We conducted a pilot study using a randomized controlled design investigating the social validity of a brief, bullying bystander program adapted to be age-appropriate for high school students (N = 65). Results indicated that high school students in the intervention group perceived the program to be acceptable and relevant and reported greater increases in knowledge (?[superscript 2][subscript p] = 0.27) and confidence to intervene (?[superscript 2][subscript p] = 0.27) in bullying situations compared to students in the control group. Despite being trained in the use of four intervention strategies, students reported using two of the strategies infrequently. Additionally, we found a significant difference between the intervention and control group for only one strategy ([phi] = -0.44). This study provides partial support for the social validity of the adapted program. Implications for implementing the program at the high school level are discussed.