Tamlaght O' Crilly, "the plague monument of the O'Crillys", is a parish in east County Derry, close to Portglenone. The O'Crillys were herenarchs, (agents or stewards), of the church lands in the area in the Middle Agents. The monument is supposed to be the burial cave on rising ground above Tamlaght village. There was a church in ancient times.
The church was roofless in 1622, though otherwise, in good repair. It was ruined in the 1641 Rebellion, and remained so throughout the reminder of the 17th century. By the 1768 survey, the church was in good repair. In 1775, the parish was divided into Tamlaght O'Crilly Upper and Lower.
Tamlaght O'Crilly Upper Church is in Tamlaght O'Crilly village in Co. Londonderry, sixteen kilometres east of Maghera. The church was rebuilt in 1815, and the chancel dates from 1859. It is entred through the porch which is at the base of a louvered tower.
The interior entrance door is in memory of Arthur McCay, and James and Sarah Michael, 1980, and there is a window of coloured lattice glass in the tower.
There are three windows in the south wall, each of which has coloured lattice glass and Y tracery and no windows in the north wall.
The east window has three lights and tracery , Our Lord is in the centre, with praying figures on either side. The window commemorates Katherine Francis, wife of Canon Robert McQuaide, Rector of Tamlaght O'Crilly Upper, 1909-1956. She died in 1935. There is a small window in the south wall of the chancel.
In the sanctuary, the stone reredos behind the Holy Table commemorates Godfrey Samuel, Alicia Greene and Godfrey Greene. The east wall is panelled in stone, which extends both sides of the reredos. The first of the three sections commemorates Thomas McKay, the second, those who fell in the Great War, and the third, L.Cpl. Alston Neely who was killed in action 1918. Similarly, the three sections to the right of the Holy Table commemorate, first, William and Margery Kernaghan, second, Alice Crockett. Over the whole reredos are carved the words, "Blessing and Honour and Glory and Power be unto the Lamb". The vestry room is to the left of the chancel.
The baptistery and font are in the north-east corner of the nave. They commemorate the Rev. Henry Innes Law, Rector 1957-1963. The pulpit on the left commemorates both Canon McQuaide and the Rev. H. I. Law. The lectern is in memory of James Lennox and his son John, 1964. The prayer desk and chair in the chancel were presented by past and present parishioners, 1960. There are some chairs in the sanctuary. One of these commemorates the Rev. Maiben Cunningham Motherwell, Curate from 1826 to 1854. Another chair is in memory of Thomas and Sarah Crockett, 1960. The credence table is in memory of William and Margaret Neely, 1971. A plaque states that the Communion kneelers are in memory of Samuel and Mary McClintock and Bessie Nelson, 1995. There is a one manual Telford and Telford organ with pedals. On hymn board was presented by St. James' Church, Belfast, 1958, and the other is in memory of Bobby McClintock.