- General correspondence, 1872-1925
- Diaries and notebooks, 1875-1925
- General papers, 1886-1925
- Papers relating to South Africa, 1892-1926
- Papers relating to World War I, 1913-19
- Papers as Secretary of State for the Colonies
- Personal papers, 1885-1926
- General Printed material, 1857-1939
- Family correspondence and papers, 1824-1928
- Correspondence and papers of Lady Milner, 1900-55
- Correspondence and papers of Cecil and Maurice Headlam, 1931-40
- Photographs
The greater part of the collection relates to Lord Milner's position as High Commissioner for South Africa.