The son of a railway labourer, Tillett settled in the East End of London when he was in his early 20s. There he helped to organize, and became general secretary of the Dock, Wharf, Riverside, and General Workers' Union, about which he later wrote A Brief History of the Dockers' Union (1910). The dock strike of 1889 secured a minimum wage (6d. an hour, called the “dockers' tanner”) and a great increase in union membership. In 1921 Tillett's union joined others in forming the Transport and General Workers' Union, after which his importance diminished somewhat.