On October 3 1864, French born priest Augustine Sauzeau founded Blenheim's first Catholic Parish.
He held the first Mass in the courthouse, but immediately saw the need for the construction of a church, and sent word requesting the necessary resources. The first church was completed, and opened on September 26, 1865.
Sauzeau left NZ in 1881, but not before the church that endures to this day was constructed in 1878. The parish has had twelve churches over the years, but the current one has been the most enduring. Constructed of wood, the church has been rated as a building of significance by the New Zealand Historic Places Trust.
During the 1990s, it became evident that a major investment in a modernisation and preservation program would be necessary for the church to survive. Because of the Historic Places Trust designation, demolition was not an option. The final result, with the old church preserved, but enlarged, and with the addition of a foyer and visitor area, is a fine tribute to the architectural skills of Sir Micheal Fowler who drew up the plans for the redesign.
In addition to the church, Saint Mary's also maintains an integrated primary and intermediate school, church offices, and presbytery on the grounds.
In the redesign process, land on the west side of Maxwell Road which included school classrooms, and Saint Patrick's Hall, was sold, and the Parish property consolidated on the east side of the road.