The church's history began in 1832 when Alexander Macdonell established a mission in Priest's Mill[2] (later to be renamed to Alexandria, in honour of Macdonnell [3]) the following year, a church was built and in 1840, the mission was elevated to a parish.

In 1890, Pope Leo XIII established the Diocese of Alexandria in Ontario and named Macdonnell as bishop.

He chose St. Finnan's as his episcopal seat, elevating the church to a cathedral.

[4] The basilica houses a Casavant organ, Opus 284, installed in 1907.

[2] On February 19, 2021, Cardinal Robert Sarah, prefect of the Congregation for Divine Worship and the Discipline of the Sacraments, on behalf of Pope Francis, designated the church as a minor basilica.