The Philip J. and Mary Stack McNiff papers contain materials created and collected by Philip J. McNiff and his wife Mary Stack McNiff. Correspondence and related enclosures make up the bulk of the collection; there are also many printed materials. Correspondents are generally members of the Catholic, library, or literary communities, particularly those affiliated with Boston College, Harvard University, and other Boston-area organizations. Materials date from circa 1880-1991.

The collection is open for research.