St. Cuan’s College was established in 1949 in the East Galway village of Ahascragh. The school was started by a locally based teacher, Mrs. Mairin Mellody. The school which started with a small number of students provided secondary education for both boys and girls.

In 1959 the school was relocated to the village of Castleblakeney and was housed in a building that was originally the local police station. In 1963 the school was taken over by the Sisters of the Presentation of Mary.

In 1970 /71 land was acquired leading to the construction of what is now the main school building. This was officially opened in 1971. During school year 1986/87 new arrangements emerged with regard to ownership and management of the school. Under the Trusteeship of the Bishop of Elphin, a Board of Management was established and a new Principal, Mr. Eamonn O’ Donoghue was appointed in May 1987. The school enrolment was 174.

During the late 1980′s and early 1990′s there was a gradual increase in the student population. The Curriculum was also increased to include Leaving Cert Vocational Programme and in 2001 the school added Further( Adult) Education.

In 1999 the school celebrated its 50th Anniversary. This event led to new moves to obtain Government funding for a programme of development. Again substantial funds were raised locally. Due to a substantial capital grant from the Department of Education & Science six new classrooms were added and a lot of work was carried out on the existing building. Due to further work locally and with the Department, two new science labs will be opened in 2009.

In 2001 the school introduced the Transition Year Programme which provides students with a general course of study in between Junior and Senior Cycles.

In the late 1990′s with the support and resources of County Roscommon Youth Service a Library and Information Centre was established.

In 2007 Mr. Eamonn O’ Donoghue retired from the position of Principal and was replaced by Mr Mattie Giblin.