The Armagh Diocesan Registry archive comprises 409 volumes and around 17,655 documents relating to the primacy, the province and the archdiocese of Armagh, 1240, 1291 and 1360 to 1977.
- archbishops' registers, 1360 to 1543, 1678 to 1719, and 1878 to 1943
- historical compilations, 1360 to 1774, which include rent rolls relating to church lands, inquisitions
- correspondence 1615 to 1957, relating to schools and education, mainly in the archdiocese of Armagh, including Armagh Royal School and the Erasmus Smith endowment
- correspondence, legal papers, accounts 1713 to 1934, relating to various charities such as Hugh Boyd's Charity, the Vaughan Charity and Jackson's Charity
- visitation returns and papers, 1617-1973
- title deeds, leases, rentals, maps, and surveys relating to church lands, 1606 to 1910