Montfort Secondary School first began in a humble way. Sometime after the outbreak of World War I, Father Laurent, Parish Priest of Serangoon, laid between the parish church and his presbytery the foundation of a two-storeyed building for a school. His successor, Father H Duvelle, started a Chinese class began on the ground floor of the newly completed building and an English class on the top floor, engaging Mr Lee Ah Kow to run the classes.
From 1922 to 1936, Mr PA D’Costa was recruited to be Principal of Holy Innocents English School and the school grew from strength to strength. In 1936, Mgr A Devals, the Bishop of Singapore and Malaya invited the Brothers of St Gabriel to run the Parish School. Brother Gerard Majella, Brother John de Breboueuf, Brother Francis Tessier and Brother Louis Gonzaga were some of the first Brothers to arrive in Singapore to start up the Gabrielite approach to education.
World War II interrupted the running of the school but immediately after the war, Brother Louis Gonzaga returned from Bahau, Johore to resume the running of classes. Numerous extensions were made. By the 1960s, Holy Innocents English School was synonymous with quality education provided by the Brothers of St Gabriel in the Upper Serangoon District.
In 1958, Holy Innocent’s English School was renamed Montfort School in order to prevent administrative confusion which had grown between Holy Innocents Boys School, Holy Innocents High School and Holy Innocents English School. The name was selected to honour St Louis Marie Grignion de Montfort.
In 1984, the Old Montfortian Association (OMA), led by its President, Mr Lim Boon Heng, accepted the challenge put to it by the School Management Committee to rebuild Montfort School to make it comparable to the new government schools. A building fund committee was formed to raise the $5.5 million necessary to finance the building project.
The ground breaking ceremony at the new site at Hougang Avenue 8 was officiated by His Grace, Mgr Gregory Yong on 12 August 1989. On January 1992, Montfort School started functioning from their new premises. At the end of 2009, Montfort Secondary School underwent the Programme for Rebuilding and Improving Existing Schools (PRIME). On January 2012, Montfort Secondary School returned to Hougang location.