In 1908 Abbott became director of the newly formed Immigrants' Protective League, Chicago, and lived for a time at Hull House, the pioneer settlement house founded by Jane Addams, with whom she was closely associated. In a series of weekly articles ("Within the City's Gates," 1909-10) in the Chicago Evening Post, she attacked the exploitation of immigrants. Later she wrote The Immigrant and the Community (1917).
As director of the child-labour division, U.S. Children's Bureau (1917-19), she administered the first federal statute limiting the employment of juveniles, the Keating-Owen Act (1916). This law was declared unconstitutional by the U.S. Supreme Court in 1918, but she secured a continuation of its policy by having a child-labour clause inserted into all war-goods contracts between the federal government and private industries. Subsequently Abbott was director of the entire Children's Bureau (1921-34). She worked hard to win public approval of a constitutional amendment against child labour, which was submitted to the states in 1924 but never ratified. While professor of public welfare at the University of Chicago (1934-39), she was also U.S. delegate to the International Labour Organisation (1935, 1937). Her book The Child and the State (2 vol.) appeared in 1938.