In 1960 Jebb was made a hereditary peer and as Baron Gladwyn became involved in politics as a member of the Liberal Party. He was Deputy Leader of the Liberals in the House of Lords 1965-1988 and spokesman on foreign affairs and defence. An supporter of the European Union, he served as a Member of the European Parliament 1973-1976 where he was also the Vice-President of the Parliament's Political Committee. He tried to be elected to the European Parliament in 1979.