The church comprises a continuous chancel and aisleless nave, a N transept with an E aisle, a S transept (originally a separate chapel) with an E chapel and S porch, and a W tower capped by a 14thc. 'Rhenish Helm'. The tower was erected in three 11thc. campaigns: the lower stage is pre-Conquest, the first and second storeys c.1066-80 and the third storey c.1080-1100. A N doorway demonstrates that vestiges of the nave belong to the first half of the 12thc., but the transepts and chancel were erected after 1154, when the church was acquired by the Templars. The church underwent extensive restorations in 1853, when most of the internal masonry was scraped under R. C. Carpenter. The interior contains a number of fragments ascribed to the 11thc., and a plain 12thc. font.

The church at Sompting (Svltinges) was mentioned in the Domesday Survey, at which time Sompting had a population of approximately 60. At that time the W tower, begun soon after the Conquest, was probably nearing completion. In 1154 William de Braose granted the church to the Knights Templar, reserving the life interests of two priests there (VCH, 61).

While the ground storey of the W tower is thought to be the W end of a pre-Conquest nave, it is generally considered that the upper three storeys, including the string course between the ground and first storeys, were raised c.1080-1100, with the strong likelihood that the gabled third storey was erected shortly after the completion of the first and second storeys (Gem 1983; Aldsworth 1988).

It has been convincingly argued that the jamb and shaft capitals of the E tower arch were carved for two separate works: Aldsworth (1988) suggested that the jamb stones were reused from 'a font or more likely a chancel arch, on this site'. He thought that they would all have originally measured h. 0.25m x l. 0.50m x d. 0.20m, but that some were trimmed, especially the E side of the S block. However, both jamb and shaft capitals find parallels in the second-storey shaft capitals on the exterior of the tower. While the tiered capitals of the E arch are similar to the N face capital, the fat stems containing fruit on the E arch jambs closely resemble the motif on the right side of the E face capital. Aldsworth has demonstrated that the tower arch was inserted when the upper storeys of the tower were built, and similarities between the sculpture of that arch and the capitals of the third storey strongly imply contemporary production by a single workshop: the spolia theory must be rejected. Other sculpture on the first and second storeys of the tower belongs to the same stylistic group. Aldsworth has drawn attention to technical similarities between the tower string course and the capital carved with tiered, hollowed leaves which stands at the beginning of a tradition culminating in the late 12thc. capitals of Icklesham, Steyning, Bexhill and other Sussex churches. The volutes on the first-storey N window jambs can similarily be compared with the capitals carved with curling stems enclosing fruit and the voluted W face shaft capital, which does not enclose fruit. Volute capitals were introduced from Normandy after the Conquest: the Sompting capital is typologically less advanced than the volute capital surviving from Battle Abbey, usually dated c.1080-1090, and with the rest of this ensemble may be dated c.1066-1080.

The slightly later capitals of the third-storey N windows are of a different type to those of the E tower arch and second-storey shaft capitals. In their conflation of volutes and shields, they combine cushion and volute capitals, and probably date c.1080-1100.

The majority of the reliefs inside the church were probably also carved towards the end of the 11thc. The three fragments of arcading, like the long volutes of the W tower third-storey N windows, retain residual Ringerike influences but otherwise the reliefs bear no stylistic relationship to the sculpture of the tower. It is possible that they formed an item of church furniture, eg: a chancel screen, which was already dismantled by the early 13thc. when the Christ in Majesty relief was carved on the backs of old panels.

The N and S doorways seem to date from the second quarter of the 12thc. The N doorway seems to have been reset incorrectly in the flint-faced wall, and has several elements comparable to the S doorway, eg: impost and label profiles, and the use of label head-stops.

The relief of a nimbed figure is iconographically close to a relief from Ivychurch (Wilts), dated c.1160, in which St Paul is shown standing in front of a lectern. At Sompting the lectern seems to have been misunderstood by the sculptor, as does the gesture of the figure. While at Ivychurch the right hand holds a pen, at Sompting it less appropriately adopts the gesture of blessing. A date in the second quarter of the 12thc. is supported by the form of the capitals on the relief, which find parallels in the nave of Steyning, and by the drapery which is a heavily stylized version of clinging damp-fold, a Byzantine-inspired technique which is absorbed into English sculpture in the middle of the 12thc. at the earliest. The capitals of the S transept chapel, built for the Templars after 1154, belong stylistically to the last quarter of the 12thc. and, finally, the N transept aisle, with its stiff-leaf bosses, probably dates from the very end of the century.