On the 5th October, 1931 a new All Irish Secondary School for boys was opened in No 6 Harcourt Street in Dublin.
This school was named Cólaiste Mhuire under the trusteeship of the Christian Brothers. The school retained in its temporary location for 2 years. In 1933 the school was relocated to no 25 Parnell Square and due to the rapid expansion of the school No 23-28 Parnell Square were occupied by the school over a period of time.
Due to the demand for places in the school a private preparatory school was established in 1938 to prepare boys for entry to Cólaiste Mhuire. This private preparatory school for boys aged 7-12 thrived until the late 1980's. At this stage numbers dwindled due to a lesser demand for private primary education and a growing trend in the establishing of all Irish Primary Schools all over Dublin. At this stage the trustees (The Christian Brothers) decided to close the private preparatory school due to lack of funding. A group of parents in the school felt that this was a terrible blow to Irish and to the education being provided in the school. This group of parents set up a primary school for boys (aged 4-12) under the Department of Education and SKills in September 1988. The schoolwas named Gaelscoil Cólaiste Mhuire.
Initially the school was granted temporary recognition but due to the demand for places in the school and its subsequent growth, the school was granted permanent recognition in 1991. In 1996 the school became co-educational.
Due to the poor condition of the buildings in 23-27 Parnell Square, the school was requested to relocate to temporary accommodation until a suitable permanent site could be identified. The primary school relocatedto No 7 Parnell Square east in 2000 and awaits a suitable permanent location for the school.