Sion College was founded under the will of Thomas White (d. 1624), Vicar of St. Dunstan-in-the-West, as an association of the clergy in the city of London. White's executor, John Simson, extended the original scheme to include a Library. Printed books and manuscripts began to be assembled from 1629. The Library grew rapidly, and already held a substantial collection by 1650 when its catalogue was first printed. The Fire of London in 1666 brought severe losses, including many English and Latin manuscripts, but the Library recovered and continued to expand until its closure in 1996.
The Sion College manuscripts are arranged by language, comprising English (234 vols, 6 boxes, 2 files), French (1 vol), Greek (14 vols), Hebrew (3 vols), Latin (45 vols), and Oriental (21 vols).
Additional manuscript items are bound amongst the printed books and pamphlets of Sion College.