This paper uses the case of Mexico to explore the effects of electoral systems on women’s representation in legislatures. While a number of studies have looked at how electoral rules affect women’s presence in parliament (descriptive representation), less work has focused on how these rules affect female legislators’ inclination to promote policy directed toward women as a constituency (substantive representation). Mexico’s mixed member electoral system serves to compare legislators operating within the same cultural, institutional and political context but who were elected under distinct electoral formulas, either through the local popular vote in single member districts (SMDs), or through proportional representation (PR) on the basis of party lists. A quantitative approach is adopted to explore the differences between the two groups when it comes to introducing legislative proposals related to women’s rights and gender equality. Based on data from the Mexican Chamber of Deputies covering a time span of 20 years, the results show that female legislators elected through Mexico’s PR tier are more likely to put forward bills on these issues than their SMD elected counterparts, independently of their party identification and where in the country they belong geographically. This suggests that the design of the electoral system can have an impact on legislative behavior, in this case that of female politicians when it comes to advancing women’s rights policy.