There have been many changes to the church, internally and externally, over the centuries. The first extension was about 1280–1300 when the north aisle was added. Between 1360 and 1380 the south aisle was added and around this time the tower was also built. The Bold Chantry (or Chapel) was added in 1406 and in 1431 the east end was extended. In 1500 the Cuerdley chapel was added to the south of the church. This was provided by Bishop William Smyth to allow his tenants in the village of Cuerdley to attend mass without coming into contact with the people of Farnworth at a time when plague was prevalent in the area. At a restoration in 1855 the nave, the north aisle and the Bold Chapel were rebuilt, the east end of the chancel was restored and the north side of the church and the vestry were repaired. A new roof was added to the nave. Galleries were built and the organ was moved into the gallery on the west wall. This restoration was carried out by William Culshaw. Farnworth became a separate parish in 1859. The last major internal restoration took place in 1894–95 when the galleries were removed and the plaster was stripped from the walls. Two new vestries were erected on the north side of the chancel and a new organ was installed. This restoration was carried out by the Lancaster architects Paley, Austin and Paley at a cost of £4,011 ().