In this study, we use a randomized control trial to examine whether asking Vietnamese men to reflect on gender equality can reduce their gender bias. We randomly selected two groups of married men in four rural provinces and asked the first group to make comments on gender-related laws and the second group to write stories about gender equality. We find that commenting on gender-related laws does not reduce men’s bias against women, while writing stories has a strong effect on reducing prejudice against women. Writing stories increases the index of gender attitudes of men in the second group by 0.29 standard deviations. The assignment also has a small effect on their contribution to housework. Changing men’s behaviour in practice requires stronger and more sustained interventions.