In 1954 Archbishop Liston invited the Rosminian Order to establish a Diocesan School on the North Shore and in 1961 Fr. Phillip Catcheside, Fr. Bill Curran, Br. John Tedesco and Br. Eric Willett arrived in New Zealand to staff Rosmini College.
In 1962 Fr. Catcheside became Headmaster of a school with six classrooms, 125 pupils and four teachers, and remained as Headmaster until 1972.
In 1976 Mr Tom Gerrard was appointed Headmaster - the first lay Headmaster to be appointed in a New Zealand Catholic school. Fr John Moss was appointed Spiritual Director.
In 1981 the Integration Agreement was signed with Mr Merv Wellington, Minister of Education.
In the 21st century the school has expanded its facilities to include the Sormany Science Centre, Tindall Auditorium, Peter Maire Technology Block, Tom Gerrard Gymnasium, John Copson Sports Pavillion, and the Mary Thomas Building in 2020.
In 2015 Nixon Cooper was appointed as the school's sixth Headmaster. Today the school has a roll of around 1100 and 70 teachers.