The library houses important collections relating to Irish history, the Irish language, ecclesiastical history, the Irish abroad and Irish Sport. It is the designated centre for Roman Catholic records for the Archdiocese of Armagh.
Cardinal O’Fiaich’s papers and books form the nucleus of the collection with substantial additions from the records of the archdiocese of Armagh.
The core of the Library consists of approximately 40,000 published volumes and 450 periodical titles dating from as early as the 15th century.. The archive contains just less than one kilometre of document storage, housing about one million documents.
The largest collection, the Irish Overseas Archive, contains items of historical and genealogical interest on Irish families in Europe from the 16th until the 19th century.
The manuscript collection preserves several important Irish language sources for poetry in South Ulster and the sports collection holds a vast collection of match programmes for Gaelic games along with historical records, artefacts and other publications.
The library and archive is an independent trust and can be accessed and used free of charge. Conference facilities and a genealogy service are available on request.