The Church of the Holy Rosary was dedicated on Sunday 7th October 1901. However, plans for a new church went back to the 1860s. Archbishop John Mc Hale laid the foundation stone for the new church in 1872 on an elevated site directly across the road from where this church stands. The original church was built to roof level but then, due to lack of funds and a clerical dispute, the work was incomplete for 20 years. A new parish priest, Canon Patrick Lyons, decided in 1891 that he would not complete the church and proceeded with a brand new build on the other side of the street.
There was huge local upset with these plans as many had contributed to the original building. They were also public meetings, many of them reported violent. Some donors demanded their money back while workers refused to work and attendances at mass dropped. However, Fr. Lyons continued with the new church and work started in 1897 with it completed in 1901 despite a portion of the building being damaged by storm during the build.
The church underwent extensive repairs in 1943 and again in 1985. The organ was replaced in 1948 at a cost of £3000 as the previous organ was disposed of in 1943 after an infestation of a woodboring beetle. Well-known local musician, Stephen Garvey, organised a series of concerts and musicals to raise the money to pay for the new organ.
There used to be beautiful, ornate gates at the entrance to the baptismal font that were made by J. Fagan & Sons (Dublin) that are no longer there. There is a Castlebar saying, that as a baby if you did not "go through Fagan's gates", you were not considered to be true Castlebar "old stock".
Canon Lyons was also responsible for bringing the religious order, De La Salle, to the town.
