The De La Salle Brothers came to Dundalk in 1899 to take charge of the Castletown Boys’ National School. In 1914 the present boys’ primary school was built. The De La Salle Monastery was built in 1902.
De La Salle College, Dundalk was originally established in 1938 as a “secondary top” school and became a fully recognised secondary school in 1970, from then to be known as De La Salle College, Dundalk.
A site for the new school was purchased from the St. Louis Sisters and building commenced in 1977. In November 1978 the teachers and students moved out to the current site. A new sports field/football pitch was added in 1982 and a full size gymnasium was built in 1984. In 1998 a fourteen-room additional building was constructed and it opened in May 1999. The most recent addition, comprising technology suite, a fourth science laboratory, four classrooms, toilet and office facilities was constructed in 2013 and was opened in 2014.