In 1905 Harraden joined the Women's Social and Political Union (WSPU). Millicent Fawcett, like other members of the National Union of Women's Suffrage Societies (NUWSS), feared that the militant actions of the WSPU would alienate potential supporters of women's suffrage. However, Fawcett and other leaders of the NUWSS admired the courage of the suffragettes and at first were unwilling to criticize members of the WSPU. In October 1906 Anne Cobden Sanderson, a former leading figure in the NUWSS, was arrested, along with members of the WSPU, Mary Gawthorpe, Charlotte Despard and Emmeline Pankhurst, in a large demonstration outside the House of Commons. After Sanderson's release the NUWSS organized a banquet at the Savoy on 11th December. Harraden sat between Minnie Baldock and Annie Kenney at the banquet.
In 1908 Harraden joined the Women's Writers Suffrage League (WWSL). The WWSL stated that its object was "to obtain the vote for women on the same terms as it is or may be granted to men. Its methods are those proper to writers - the use of the pen." Women writers who joined the organisation included Cicely Hamilton, Elizabeth Robins, Charlotte Despard, Alice Meynell, Margaret Nevinson, Evelyn Sharp and Marie Belloc Lowndes. Sympathetic male writers such as Israel Zangwill and Laurence Housman, were allowed to become "Honorary Men Associates".
In March 1908 Harraden read a chapter from Ships That Pass in the Night at a WSPU fund raising event. She also shared the platform with Christabel Pankhurst at a meeting of the WSPU in Hampstead in March 1910. She also wrote several articles for Votes for Women. She joined the Tax Resistance League and refused to pay tax on her royalties until women got the vote.
Harraden left the WSPU during its arson campaign. She was also concerned about the health of hunger-strikers such as Emmeline Pankhurst and Lilian Lenton. She complained to Christabel Pankhurst, now living in exile in France, for risking the health of her members.
Beatrice Harraden died on 5th May 1936.