The James Spencer Northcote papers primarily consists of correspondence between Northcote and John Henry Newman, Richard Simpson, James Burns, and Father Ambrose Rose St. John, during the years that Northcote served as acting editor of The Rambler. The correspondence mainly relates to articles published in The Rambler. Of particular note are letters written by John Henry Newman to Northcote expressing his unhappiness with how the Church in Rome views English converts. Other correspondence from Newman relates to Northcote's editorship of The Rambler.

The remainder of the collection consists of a notebook with Northcote's sermon drafts, as well as a few sermons given by others. The front and back covers contain lists of his "Occasional sermons" as well as those he gave at St. Mary's School, Oscott in England.