The main goal of this study is to develop a virtual reality (VR)-based scenario of bullying that is more effective in investigating the motivational factors (i.e., emotion, self-efficacy) of adolescents' bystander behavior than the traditional text method. The second goal is to examine how emotion and defender self-efficacy relate to adolescent bystander behavior. Eighth graders (N = 229) from Taiwan participated in 2 (presentation mode: VR vs. text) x 2 (participant sex: boys vs. girls) x 2 (actor sex: boys vs. girls) experimental trials. The results of MANCOVAs indicated that boys displayed less outsider and pro-bullying behavior in the VR group than in the text group; however, there were no differences in bystander behavior for girls. The subjects in the VR group experienced more fear and excitement, less empathy, and a lower level of defender self-efficacy than those in the text group. The results of regression analyses showed that higher levels of anger and defender self-efficacy significantly predicted positive bystander behavior. Qualitative data revealed that VR provided the subjects with a vivid and realistic bullying experience and enabled them to experience emotions such as anger, empathy, and fear. The findings demonstrate that VR increases students’ antibullying attitudes, justice emotions, and positive bystander behavior. However, VR does not provoke more empathy and self-efficacy, as expected. VR might capture a different dimension of response to bullying than the traditional text method. Nevertheless, VR has promise as an educational tool for developing bystander intervention in high school.