Herbert joined the Diplomatic Service, and was posted to Paris, aged 21, on 1 June 1879, where he was appointed Third Secretary in March 1880, and Second Secretary in November 1883. Herbert was trained in the diplomatic service by Richard Lyons, 1st Viscount Lyons,[3] then British Ambassador to France, and was a member of the Tory-sympathetic 'Lyons School' of British diplomacy.[4]
Herbert was transferred to Washington DC on 31 August 1888, where he served as Secretary and twice acted as Chargé d'affaires. In September 1893 he transferred to The Hague, and in August the following year was promoted to Secretary of Embassy at Constantinople. He was appointed a Companion of the Order of the Bath (CB) in 1896. Following a brief posting to Rome in 1897, he was appointed Minister Plenipotentiary in Paris in 1898.[5]
As ambassador, he created with the U.S. Secretary of State John Hay a joint commission to establish the border between the U.S. district of Alaska and British interests in the Dominion of Canada, where gold had been found in the 1890s, which resulted in the definitive Alaskan boundary treaty of 1903. He was also involved during the Venezuela Crisis of 1902–1903.