[2]: 128  Ecclesiology held that new church buildings should imitate those of the 13th and 14th century Decorated Gothic period, which displayed three essential characteristics lacking in Fredericton's existing wooden parish church: "reality", which meant that the building's structural elements such as rafters must be visible; a large chancel clearly separate from the congregation; and open bench seats rather than box pews.

[3]: 15 Medley chose the 14th century St. Mary's Church in Snettisham, Norfolk as the model for the new Fredericton cathedral.

[5] The Ecclesiological Society's newsletter, The Ecclesiologist, took issue with Medley's choice of St. Mary's, "though magnificent as a parish church", as his model.

In the course of construction, the roof heights were equalized, and other modifications were made either for economic reasons or because of the limited skills of local artisans.

[5]: 97  However, Medley consistently followed the ecclesiological practice of finding authority for all the architectural details in one or another existing English Gothic church.

[3]: 15  Medley chose a site beside the Saint John River, near the existing parish church, and was given 2.5 acres (1.0 ha) by the landowner.

[6]: 112  Site preparation work began in August, and the cornerstone was laid by Lieutenant Governor William Colebrooke on 15 October 1845.

He also designed and oversaw the building of St. Anne's Chapel of Ease, which Medley had built in order to hold services while the cathedral was under construction.

[2]: 130 The cathedral's nave and aisle walls were completed by the end of 1847, but further work was delayed by lack of funds.

Bishop Medley returned to England for several months in 1848 to raise more money and to consult with the Ecclesiological Society about how to proceed, since Frank Wills had left Fredericton in early 1848 to set up an architectural practice in New York City.

[2]: 132  On the recommendation of the Ecclesiological Society, the British architect William Butterfield designed a choir and tower, and Medley succeeded in raising a further £2,000.

[3]: 19  In 1851 Medley visited the United States and England, raising more funds and receiving donations of cathedral furnishings.

A narrow spiral staircase of 51 steps must be climbed to access the room housing the clock and bell mechanisms.

Its tracery is a copy of that in the east window of Selby Abbey, and its seven panels depict Christ and six of his apostles.

[8]: 47 The cathedral was struck by lightning on 3 July 1911, causing a fire that completely destroyed the spire.

[3]: 29 In the 1990s the cathedral underwent a $2.5 million restoration consisting of refacing its stonework, repointing tracery, cleaning its woodwork, refinishing of pews and shoring up the masonry on the east end.

[10] A fire in the bell tower on 6 August 2006 activated the sprinkler system, causing water damage to the choir area.

St. Anne's is the former Chapel of Ease constructed by Bishop Medley upon the demolition of the original parish church on the present cathedral site.

The incumbent since September 2024 is Geoffrey M. Hall, formerly diocesan archdeacon and executive assistant to Claude W. Miller, ninth bishop of Fredericton.