Building on recent research, this paper recounts the emergence of Catholic women’s activism in favor of the right to abortion in late twentieth-century Mexico. The article argues that contests over legitimacy—specifically, disputes among Catholics about which beliefs are legitimately Catholic—are central to this history. In this case, the article follows Catholic women’s attempts to legitimize their position in favor of the right to abortion and Catholic authorities’ attempts to delegitimize the same idea. The paper concludes with a 1992 episode in Guanajuato that has not received much scholarly attention, when secular and Catholic feminists collaborated. Because these Catholic activists faced opposition from angry protestors, they set up a press conference to dispel any misconceptions and legitimize their own Catholic position in favor of the right to abortion to the Mexican public. The resistance Elvia Neri, a retired Catholic woman and mayordoma for her church, faced led her to share her testimonio, a rare archival source that publicly reconciled a commitment to both the Catholic faith and reproductive rights. Scholarship on feminist mobilization has at least included the work of Catholic activists who advocated the right to abortion. However, these contests over legitimacy have led scholarship on Catholic women’s activism to neglect Catholic perspectives that favor the right to abortion.