When Pococke became bishop of Ossory, he appointed Archdall his domestic chaplain, bestowed on him the living of Attanagh (partly in Queen's County and partly in County Kilkenny), and the prebend of Cloneamery in the cathedral church of Ossory (1762), which he afterwards exchanged (1764) for the prebend of Mayne in the same cathedral.
Archdall was also chaplain to Francis Pierpoint, Lord Conyngham, and a member of the Royal Irish Academy.
His major work is Monasticum Hibernicum; or, An history of the abbeys, priories, and other religious houses in Ireland.
The publication of a new edition, entitled Monasticon Hibernicum, with notes by Patrick F. Moran and other antiquaries began, in parts, at Dublin in 1871.
He also produced an edition of John Lodge's Peerage of Ireland, 'revised, enlarged, and continued to the present time,' (7 vols.