The parish church of St. Mary was extensively rebuilt in 1846. Fragments of an earlier building remain, suggesting a church had been built by 1300. The east window of the chancel survives from this period and there is a blocked 14th century niche over the doorway to the porch.
Very little information concerning the early history of this church has survived. However, during the late 18th century, detailed notes concerning repairs to the church were written on the inside cover of the parish register. In 1763, for example, the paving and wooden panelling in the chancel were renewed, the pews painted and the windows repaired. In 1765 the nave was newly paved and a new font installed. In 1766 a new pair of stocks was set up. Three years later the chancel was opened up into the church. 1775 saw the purchase of a new church clock.
During this time the curate at Wylye was John Eyre. He dedicated his life to this parish, spending 33 years here. The parish register notes that he died in 1792 after a long and severe illness born with 'true Christian resignation'. He hardly ever missed a Sunday service. When Eyre completed the Bishop's Visitation Return in 1783 he stated that he could remember being absent 'only one Sunday in almost three and twenty years'. This return gives a glimpse of life in an 18th century Wiltshire parish. There were two services each Sunday; prayers at 10.30 a.m. followed by prayers and a sermon at 3.00pm. There were also services on Wednesday and Friday and all holidays and festivals. Holy Communion was administered six times a year. There were no non-conformists in Wylye at this time.
The church was visited by Sir Richard Colt Hoare in 1824. At this time the church consisted of a tower, nave and chancel. The building measured 76 feet long by 17 feet inches wide. The font was at the west end near the tower.
By the early 1840s thoughts were turning to the building of a new church. The faculty dated 10/6/1844 declared the church to be in a 'very ruinous and dilapidated state'. It was also too small, being able to accommodate just 200 people out of a population of 508. Only the tower and the walls of the chancel were retained, the rest was demolished and rebuilt. The new church was completed by 1846, with an additional north aisle and a porch around the south door. The font was just inside this entrance. The architect responsible for the rebuild was T.H. Wyatt and the total cost was £1126.16s. The parish raised £200. Donations included £400 from the Pembroke family, £100 from the Duke of Somerset, and £135.11s.1d given by the Rector and some of his friends. The new church had seating for 312 people.
Inside the church, the nave and the north aisle are divided by octagonal pillars. The pitch pine pews date from the rebuild, but the doors to the pews were added shortly after. This extra feature was requested by the owners of appropriated pews and was paid for by an additional church rate. The pulpit, lectern and prayer desk were taken from the church at Wilton when it was demolished and were given to Wylye by the Earl of Pembroke. All three pieces are of richly carved oak and the pulpit dates from 1628. The lectern may have been made out of panels that were originally the door to the pulpit.
The font was given in 1846. It replaced the old font, dated 1765, which is now also in the north aisle and has a sundial on top. It was moved indoors from the churchyard to help preserve it. In 1876 a new organ was built, to replace the one installed in 1851. At the same time the vestry room was enlarged and an archway formed between the vestry and the chancel. The font was moved from the south wall near the door to its present position in the north aisle. Lastly, a new oak screen was placed between the tower and the nave.
Until 1975 this church had five bells, the oldest of which was cast in 1587. An inspection in 1973 revealed the bells to be in reasonable condition but the condition of the fittings had deteriorated so badly that it was no longer safe to ring the bells. Funds were raised to enable the bells to be restored and rehung in 1975. At the same time the five bells were augmented to six with the addition of a new treble bell that was in Fisherton-de-la-Mere church.
The churchyard has one particular monument of interest. In the 18th century a man named Popjay was convicted of a serious crime and transported. He returned to Wylye c.1810 an apparently wealthy man, lodging at The Bell Inn. He was most upset to find that his mother and sister had both been buried in pauper graves. He ordered a vault to be built and had his relatives reburied. When the bill arrived, Popjay disappeared and it was left to the unfortunate rector to pay. Having paid for the tomb, it is believed that the rector asked to be buried there himself.
In 1957 the church at Stockton was added to Wylye parish. In 1973 The Langfords were added and in 1982 the parish was known as Yarnbury. In 1997 this group of parishes was renamed the Wylye and Till Valley Team.
The parish registers dating from 1581, apart from those currently in use at the church, can be seen at the Wiltshire & Swindon History Centre in Chippenham.