Background. Dutch universities struggle to find effective evidence-based intervention tools to reduce the high prevalence of sexual violence among their students. Reducing sexual violence means a safer student climate and thus better inclusion of women and more diversity in higher education. Interesting approaches to consider for cultural change are bystander intervention and an already existing co-designed serious game. This game aims to encourage a dialogue among students but has thus far not been evaluated on its effectiveness. Therefore, the goal of this study was to evaluate how a serious game can promote an intergroup dialogue between female and male students in Dutch universities to encourage bystander intervention in situations of sexually transgressive behaviour. Methods. Literature research and brainstorm sessions with female and male students from Delft University of Technology (TU Delft) were conducted to gain a better understanding of sexual violence among students. These methods were used as part of participatory game design research. Moreover, a quasi-controlled experimental trial was conducted with 64 TU Delft students from different nationalities and study backgrounds to evaluate the serious game on bystander attitudes, sexual violence myth acceptance, the willingness to intervene, and the effectiveness of the intergroup dialogue. Results. The results showed that the serious game session has a significant positive effect on bystander attitudes (i.e. bystander awareness and responsibility) and the willingness to intervene. No significant difference was found in sexual violence myth acceptance. Additionally, the game proved to promote an effective intergroup dialogue between the participants. Conclusion. Serious gaming proved to be effective in encouraging ethical bystander behaviour by promoting an intergroup dialogue. Therefore, universities are recommended to use serious games as an intervention tool to contribute to cultural change. Future studies should include students from other universities and focus on minimising selection bias to research whether serious games can also influence sexual violence myth acceptance.