Douglas Sladen was educated at Cheltenham College, and later Trinity College, Oxford, where he received a Bachelor of Arts in 1879. After moving to Victoria - where his uncle Sir Charles Sladen had been premier - he attended the University of Melbourne, attaining a Bachelor of Laws in 1882.
In 1880, Sladen married Margaret Isibella Muirhead, with whom he had a son, and after her death in 1919 married Dorothea Dulthie in 1930. He developed friendships with George Morrison and John Monash, whose Australian Victories in France (1920) he helped edit. In 1883 Sladen moved to New South Wales where he was appointed the first lecturer in modern history at the University of Sydney, and in the same year became a foundation member of the New South Wales branch of the Australasian Geographical Society.
After his return to England in 1884 Sladen continued to develop his interest in Australian poetry, particularly the works of Adam Lindsay Gordon (q.v.). He published editions of Gordon's poetry as well as biographical material, and became secretary of the memorial committee responsible for placing Gordon's bust in Westminster Abbey in 1934. He also compiled and edited important and influential anthologies of Australian verse.
In 1897 Sladen worked on editing Who's Who and broadened its coverage of prominent people. Although he never revisited Australia, he produced an edition of Billy Hughes's pamphlets and speeches, From Boundary Rider to Prime Minister (1916), and also continued to write books with Australian themes, such as Fair Inez (1918), set in Australia in 2000 A.D., and Paul's Wife, or, 'The Ostriches' (1919), which portrayed a fictional Alfred Deakin (whom Sladen had known in Melbourne) in retirement in England.
After his return to England, Sladen wrote many novels, travel books and political and historical works, including (but not limited to) the following: The Spanish Armada (1888), My Son Richard, or, The Great Company (1901), The Tragedy of the Pyramids (1909), Germany's Great Lie (1914), Grace Lorraine (1919), A Japanese Marriage (1895), Carthage and Tunis 1906), and Meriel Brede Secretary(1935). He also wrote a novel, Seized by a Shadow [1897], under the psuedonym 'Rose Mullion'.
Please note that only those works with Australian themes and settings have been assigned a record in AustLit.