The Seminary was initiated under the first bishop of Ottawa, Monsignor Joseph-Bruno Guigues, a member of the Missionary Oblates of Mary Immaculate. The Seminary remained under the guidance of the Oblates into the early 1900s.
In 1924, Monsignor Joseph-Menard Emard, then Archbishop of Ottawa, decided that the direction of the diocesan Seminary should be in the hands of the diocesan clergy.
In the spring of 1925, the former Protestant General Hospital at the corner of Rideau and Charlotte Street was purchased by the Archdiocese of Ottawa, and the building was converted into Minor and Major Seminaries. The Catholic Seminary of Ottawa was founded in 1925, and the senior seminarians began studies on 15 September of that year.
The Minor Seminary provided eight years of classical schooling leading to a Baccalaureate of Arts. The Baccalaureate graduates could then complete a further four years in the Major Seminary, graduating as priests.
In 1943, the Archdiocese separated the Seminaries and moved them to other sites in Ottawa. The building was purchased by the Navy in 1943 and was converted into barracks for the Women’s Royal Canadian Naval Service.