Astor was a supporter of the coalition government established by David Lloyd George in the First World War. In January 1917 he was appointed as the prime minister's parliamentary secretary. In July 1918 Astor became parliamentary secretary to the Ministry of Food.
On the death of his father in 1919, Astor became a member of the House of Lords. His wife now became the party's candidate in the resulting by-election. Nancy Astor beat the Liberal Party candidate, Isaac Foot, and on 1st December 1919 became the first woman to take her seat in the House of Commons (the first woman to be elected was Constance Markievicz in 1918 but as a member of Sinn Fein had disqualified herself by refusing to take the oath).
Astor remained in the government and served as parliamentary secretary to the Local Government Board (January 1919 to June 1919) and parliamentary secretary to the Ministry of Health (June 1919 to April 1921).
Astor became proprietor of The Observer in 1919. He also served as a governor of Guy's Hospital and of the Peabody Trust. Other posts held by Astor included Chairman of the Royal Institute of International Affairs (1935-1949) and Lord Mayor of Plymouth (1939-44).
Waldorf Astor, died on 30th September 1952.