The site of the present building of Bangor Cathedral has been in use as a place of Christian worship since the sixth century.

The cathedral was built on a low-lying and inconspicuous site, possibly so as not to attract the attention of Viking raiders from the sea in ancient times.

The Synod of Westminster in 1102 is recorded as taking measures to restore Bangor Cathedral, but the earliest part of the present building was built during the episcopate of Bishop David (1120–1139) with the assistance of the king of Gwynedd, Gruffudd ap Cynan, who donated money towards the project and was buried by the high altar on his death in 1137.

Rowland Meyrick, the second son of Meyric ap Llewelyn, was the first Bishop of Bangor following the Reformation and is buried under the cathedral.

Meyric ap Llewelyn was High Sheriff and Captain of the Guard at the coronation of Henry VIII on 26 April 1509.

The building as seen today is the result of extensive work carried out under the supervision of George Gilbert Scott, starting in 1868.

Scott's design originally called for a high central tower and spire, but this was never completed as cracks appeared which were thought to indicate subsidence of the foundations.

[citation needed] The cathedral also contains a number of pieces of woodwork created by Robert Thompson, including 5 of his famous wooden mice.

Previous deans include: The first extant reference to an organ in the cathedral comes in a poem by Gruffudd Gryg, who witnessed the arrival of a new instrument sometime between 1350 and 1370, and records show all the parishioners contributed towards it.

However, during the episcopate of the next bishop, Lewis Bayly, we hear of one Thomas Boulton playing the organ and complaining that his salary was not paid!

Numerous students have benefited from study at this instrument and noted organists from all over the world have visited Bangor Cathedral especially to play the organ and give public concerts.

[16] There have been many assistant organists over the years, including Arnold Lewis who became head of music BBC Wales, James Griffiths (1964–2007) and Martin Brown.