Born at Blounts Court, he was the second son of John Hiley Addington, brother of Henry Addington, 1st Viscount Sidmouth, and his wife Mary, daughter of Henry Unwin.
[2] In the next year he was appointed Secretary of Legation to Switzerland, an office he held until 1818.
[3] He executed this position again in Copenhagen in 1821, however became chargé d'affaires in Washington already a year later.
[3] Addington was promoted to plenipotentiary in London for negotiations with the United States of America in 1826,[2] and was moved to Frankfurt am Main as Minister Plenipotentiary to the German Confederation in 1828.
[2] In 1833, he returned to England and became Permanent Under-Secretary of State for Foreign Affairs in 1842.