The RSPB archive comprises all the Society's publications since its founding, including leaflets and other ephemera, annual reports from the first for 1891, together with the members' magazine Bird Notes & News from 1903, later Bird Notes, and since 1966 Birds. Unpublished material includes a set of Council and Committee Minute Books (though some of the earlier books are missing, destroyed during WW2 when the Society's then HQ in London suffered bomb damage), and a variety of miscellaneous papers, correspondence, photos and artefacts, occupying some 25 metres of shelf space. RSPB archives also hold a small collection of letters and other archive material relating to the author and naturalist W H Hudson (1841-1922) who was a prominent supporter of the Society in its formative years. Items are boxed according to subject, using an in-house classification, but individual items are not catalogued.

The UK Web Archiving Consortium is archiving the website on a regular basis.

Access to historical material (pre-1965) is normally open to researchers by prior written appointment. More recent unpublished material is also available on a discretionary basis. However, current storage facilities mean that some items may be temporarily unavailable.

There are also papers of the RSPB relating to red kite in Wales (c1903-59) at the National Library of Wales: Department of Collection Services (source: NRA). Records of the Chichester branch of the RSPB have been placed at the West Sussex Record Office (source: NRA).