There is a dearth of empirically validated pro-diversity methods that effectively create a more inclusive social climate. We developed two scalable interventions that target people's perceptions of social norms by communicating to them that their peers hold pro-diversity attitudes and engage in inclusive behaviours. We tested the interventions in six randomized controlled trials at a large public university in the United States (total n = 2,490). Non-marginalized students exposed to our interventions reported more positive attitudes toward outgroups and greater appreciation of diversity, whereas marginalized students had an increased sense of belonging, reported being treated more inclusively by their peers and earned better grades. While many current pro-diversity initiatives focus on raising awareness about the fact that implicit bias and subtle discrimination are widespread, our findings spotlight the importance of drawing people's attention to their peers' pro-diversity values and attitudes to create positive and lasting effects on the social climate.