The first building was a small wattle and daub church on the northern bank of the River Lagan.
The diocese of Dromore was established through the reorganisation of the Irish Church in the late 12th century, possibly at the synod held in Dublin in 1192 by the papal legate, Múirges Ua hÉnna, Archbishop of Cashel.
The diocese coincided with the territory of the Uí Echach Cobo, which later became the baronies of Upper and Lower Iveagh, and the lordship of Newry, County Down.
In the Roman Catholic Church, the bishopric of Dromore continues as a separate title.
The most recent Incumbent was the Most Reverend John McAreavey, Bishop of the Roman Catholic Diocese of Dromore, who was appointed by the Holy See on 4 June 1999 and was ordained bishop on 19 September 1999.