The British campaigner Maude Royden remained vice president of the international WILPF,[6] and other British members included Kathleen Courtney, Isabella Ford, Margaret Hills, Catherine Marshall, Emmeline Pethick-Lawrence, Ethel Snowdon, and Helen Swanwick.

[9][10] Richard J. Evans described the founders of WILPF as "a tiny band of courageous and principled women on the far-left fringes of bourgeois-liberal feminism".

WPP sent representatives, among them the journalist and novelist Mary Heaton Vorse, to a subsequent International Women's Congress for Peace and Freedom, held in The Hague from April 28–30, 1915.

[12] The 1915 International Congress of Women was organized by the German feminist Anita Augspurg, Germany's first female jurist, and Lida Gustava Heymann (1868–1943) at the invitation of the Dutch pacifist, feminist and suffragist Aletta Jacobs to protest the war then raging in Europe, and to suggest ways to prevent war in the future.

[14] It adopted much of the platform of WPP and established an International Committee of Women for Permanent Peace (ICWPP) with Jane Addams as president.

[5] The US branch of WILPF grew in recognition and membership during the post-WWI era, despite some attacks on the organisation as "unpatriotic" during the First Red Scare.

[15] Prior to the outbreak of World War Two, the League also supported measures to provide relief for Europe's Jewish community.

[20] As long term supporters of the Permanent Court of Arbitration, Inter Parliamentary Union, League of Nations, International Labour Organization, International Peace Bureau and United Nations, they remain a flagship organisation in the Peace Movement.