The urgent need to shift from fossil fuels to renewable energy in combating climate change is often impeded by conflicts and political polarization. Multistakeholder collaboration, which involves diverse participants working together to address complex issues, is a potential solution, but entrenched viewpoints can hinder progress. To address this challenge, we conducted an experiment testing two socio-psychological interventions—grounded in self-affirmation theory and moral foundations theory— designed to foster constructive group dynamics in multi-stakeholder settings. We recruited 1,244 students from Southern Illinois University, Carbondale to participate in an online survey about their opinions on several hypothetical on-campus sustainability initiatives. An initiative that would require students to complete a course in sustainability was found to be the most polarizing. We then invited a second sample of 282 students to discuss their views on this initiative in small groups. Prior to the discussion, each group was randomly assigned to complete one of two intervention exercises that involved a short writing task, or to a control condition. We found that groups assigned to the self-affirmation intervention exhibited significantly more openness-perspective-taking, information processing and agreement, compared to those in the control groups. Participants in groups who completed the moral foundations intervention were more supportive of the initiative overall, but showed no increase in support, openness-perspective-taking, information processing or agreement, compared to other groups. These findings provide preliminary evidence that completing a short self-affirmation intervention prior to engaging discussion has the potential to facilitate constructive dialogs on divisive issues related to sustainability.