This article traces the transformation of the International Brotherhood of Teamsters, a labor organization that had formally excluded women, but began to recruit them into membership in the 1940s. Government directives forced the temporary abeyance of the exclusionary policy during World War II, and after the war the union leadership's desire to expand the organization's size and scope led to a dramatic shift; women were then welcomed as members and promised equal treatment. Women Teamsters in this period, however, still faced discrimination and hostility from employers, coworkers, and some of the union leadership. The efforts of a group of women members in Wisconsin illustrate how female Teamsters challenged unfair treatment while acknowledging the benefits of their union. Their efforts exemplify the process of incremental change historian Alice Kessler-Harris has described and offer a window into the history of women in the more conservative American Federation of Labor (AFL) unions.