Together with Jane Addams, Balch helped to found the Women's International League for Peace and Freedom (WILPF) in 1919. The League was dedicated to freedom and the belief that people must find a way to maintain freedom without resorting to war. Primary issues for the league included universal disarmament, race equality, the rights of Jewish people, mass deportations, acceptance of refugees, and social problems such as the separation of church and state.

       Balch devoted her life to the affairs of the League. She served as the League's secretary-treasurer from 1919-1922 and then as the president of the U.S. section from 1928-1933. She traveled extensively for the League to other countries to meet and talk with women of foreign delegations about cooperating for the pursuit of peace and freedom.

       One of Balch's most important missions for WILPF was a trip to Haiti in 1925 with a WILPF delegation of six people to investigate the condition of Haiti under U.S. Marine occupation. She found that there were contrasting viewpoints between the Haitians and the Marines.

       The Marines believed they were helping the Haitians by building beneficial structures such as bridges, roads, hospitals, and schools. Haitians, though, thought it was a small curse because they no longer had a form of self-government. Moreover, their children would grow up with a sense of racial self-consciousness, fractured pride, frustration, and loss of self-respect. When Balch returned, she presented the conclusions of the group to Calvin Coolidge and submitted a memorandum embodying some of her observations.

       The WILPF existed during both of the world wars and advocated relief for the suffering masses throughout the crises. In WWI, Balch was at the forefront in trying to persuade the newly formed League of Nations to achieve peace without anymore fighting.

       During WWII, the WILPF realized that peaceful methods would not be applicable to the advancing Adolf Hitler and the Axis Powers. The organization reluctantly changed its views and supported the U.S. and its decision to go to war against Germany in hopes of ending Hitler's savage treatment of Jewish populations.

       Because of Balch's dedication to the League, it still exists today and is a force to be reckoned with. The Women's International League for Peace and Freedom is still active in its efforts to bring peace and human equality to the world. It publishes an international journal, issues reports and occasional papers, and continues to urge total and universal disarmament and has also added new goals with the changing times. Current campaign topics include protests trying to save water from corporate commercializing, anti-racism, the situation in Cuba, and the war in Iraq.

       For Balch's invaluable accomplishments to world peace, she was the third woman to be awarded the Nobel Peace Prize in 1946.