This paper examines preferences for gender diversity among co-workers. Using stated-choice experiments with 5,400 PhD students and university students in Germany, we uncover a substantial willingness to pay (WTP) for gender diversity of up to 5% of earnings on average. Importantly, we find that women have a much higher WTP for gender diversity than men. While the WTP differs by career ambition, competitiveness, and family preferences, we find that gender differences in traits and preferences cannot explain gender differences in the WTP for diversity. Our findings provide an explanation for differential sorting of men and women into high-profile jobs based on the share of female co-workers.