Using the natural experiment created by France's 2011 board gender quota law, we find that the presence of women on boards increases firms' environmental and social (E&S) performance. After the quota law, firms are more likely to create an E&S committee, and women directors are increasingly serving as members of the main board committees and as chairs of E&S committees. We find that prior to being recruited to boards, women directors have more environmental and social experience than men. Combined with their increased authority after the introduction of quotas, their E&S skills allow them to steer companies toward more E&S-oriented policies.