The roots of the modern men’s rights movement can be traced back to 1960s agitation for divorce reform and later surges of fathers’ rights activism. An overlooked feature of the movement’s growth is the activism of women. Using organizational papers, press coverage, and advice literature, this article examines self-identified “second wives,” female activists married to men who first mobilized following acrimonious divorces and child custody battles. Second wives constituted a sizable minority of men’s rights movement membership and held key leadership roles. As with women’s activism in other conservative and antifeminist political movements throughout the late twentieth century, second wives responded to both their movement’s surface demands and, at a deeper level, a threatened gender order. Second wives’ vital organizing roles also made it possible for the men’s rights movement to gain public respectability, allowing its ideology to enter the mainstream by the mid-1990s.