Worthington-Evans unsuccessfully contested the Colchester constituency in 1906. He won the seat in January 1910, holding it until 1929, when he transferred to the London seat of Westminster St George's. He served in David Lloyd George's coalition government as Parliamentary Secretary to the Ministry of Munitions from 1916 to 1918, as Minister of Blockade in 1918, as Minister of Pensions from 1919 to 1920, as Minister without Portfolio from 1920 to 1921 and as Secretary of State for War from 1921 to 1922. In 1919 he was sworn of the Privy Council.