This research identified two mechanisms that explain gender differences in attitudes towards gender quotas. Using a multi‐method approach, we assessed attitudes as self‐reported support for gender quotas and rater‐coded valence of participants’ free associations with gender quotas. Study 1 examined quotas for university professorship positions (N = 237) and Study 2 quotas for corporate leadership positions (N = 587). Supporting the first mechanism, women's greater perceptions of discrimination against women related to greater perceived necessity of gender quotas, which related to more favourable attitudes. Supporting the second mechanism, men's greater concerns that quotas discriminate against men related to greater concerns that quotas stigmatize women as incompetent, which related to less favourable attitudes. By advancing the understanding of key mechanisms behind attitudes towards gender quotas, this research contributes to effectively designing and successfully implementing hard affirmative action policies aimed at overcoming women's underrepresentation in leading academic and corporate positions.