The parish now known as St. Peter's was established 10 August 1834 and the first church was constructed of logs at the southwest corner of Dufferin Avenue and Richmond Street.

The new church was located at the northeast corner of Dufferin and Richmond, just in front of the present structure.

The Diocese of London was created in 1856 and Bishop Pierre-Adolphe Pinsoneault selected St. Lawrence as his cathedral renaming the church St. Peter's.

In 1958, the twin towers of the facade, Lady Chapel, and sacristy were added, stained glass windows were installed in the narthex and additional interior painting and decoration completed.

St. Peter's was raised to the status of a minor basilica 13 December 1961 by Pope John XXIII.