The church played a significant role in the early stages of the Oxford Movement, being the site of daily services as well as such ritualist practices as altar candles and the wearing of Eucharistic vestments.

[1] From the mid-13th century the Osney area was referred to as the parish of St Thomas', but it remained nominally a chapel of the abbey until the dissolution of the Monasteries under Henry VIII, when it was placed under Christ Church, Oxford.

[2] This boat was St Thomas' first chapel of ease; it was donated by H. Ward, a local coal merchant, and used until it sank in 1868.

[1] The vicar from 1842 to 1892 was Thomas Chamberlain (later founder of St Edward's School), a firm believer in the Tractarian movement, who introduced daily services as well as such ritualist practices as altar candles and the wearing of Eucharistic vestments – the latter causing him to be rebuked by Bishop Wilberforce in 1855.

[3] In 1847 Chamberlain founded the Community of St Thomas Martyr, which was devoted to the assistance of the poor of the parish, by now heavily slumland; this sisterhood remained active until 1958.

In November 2022, the parish began a consultation as to whether or not to rescind this arrangement, and in January 2023 the PCC voted by a majority to welcome the ministry of women priests and bishops.

[5] The church has a nave with a north aisle and vestry, a Perpendicular Gothic west tower, a chancel and a south porch.

[6] The nave was rebuilt in the late 15th or early 16th century to meet a tower of approximately the same age; it is often dated to 1521, but appears to be built on older foundations.

Underwood in 1890;[dubious – discuss] the vestry was built in the 17th century and rebuilt in 1846 to designs by Chamberlain, through the generosity of the curate, Alexander Penrose Forbes.

[1] The chancel, which has a ceiling decorated by C. E. Kempe, has three windows in the style of the late 12th century,[7] and a priest's door built into the south side circa 1250.

[1] A south porch was built in 1621 at the behest of Dr Robert Burton, whose arms are carved in the gable above the date.

The remains of an earlier Rolfe building, the 1886 Sisterhood of St Thomas, are also present; in 1974, these amounted to a single cottage and a sculptured brick gateway.