Monks Kirby has been a local centre for the Roman Catholic faith since the conversion of the 8th Earl of Denbigh to Catholicism in 1850. St Joseph's convent and girls school/orphanage were established in the village in the 1870s. The first nuns were Sisters of Charity from a convent on the Earl's other estate at Pantasaph in Flintshire, North Wales. The Sisters of Charity were succeeded by the Sisters of Mercy in 1923 who remained at the convent until 1977 In the 1982 the convent was occupied by the first congregation of Mary, Mother of the Church (now called "Mater Ecclesiae") established by Sister Catherine Mulligan as a new convent for mature women looking to enter religious life. In 1998 the Mater Ecclesiae congregation moved to Street Ashton House in the neighbouring hamlet of Street Ashton, where it was based until 2020. The remaining, elderly sisters have now dispersed and the convent sold, bringing to an end a 150 year tradition of (renewed) monastic life in Monks Kirby.