The collection includes correspondence; drafts of books, articles, broadcasts, and speeches; family papers; a diary; and photographs.

Some of the highlights of the collection include correspondence and papers relating to William Strang's career in the Foreign Office, including the Metro-Vickers trial in Moscow, 1933; Appeasement policy, 1938-9, and his relations with the Foreign Office during that period; and the work of the European Advisory Commission 1943-5, and the British Control Commission in Germany, 1945-7. There are numerous letters exchanged between William Strang and historians interested in his memories of people and events during his Foreign Office career and particularly during his time as Joint Permanent Under-Secretary (Germany Section) and Permanent Under-Secretary. Nine files of photographs illustrate different stages of William Strang's diplomatic career.

The collection includes photocopies of diaries he kept while on active service in France and Belgium, 1916-17. The originals of these diaries are in the Liddle Collection at Leeds University Library's Special Collections.