Bosham church is largely Anglo-Saxon, but the upper storey of the W tower and the first chancel extension were erected after the Conquest. The second chancel extension and the aisles are 13thc. The only Romanesque architectural sculpture in situ belongs to the upper storey of the tower, but the interior houses a font, a pillar piscina and loose architectural fragments of 12thc. date.

According to Bede, a small monastery with five to six monks led by Dicul existed at Bosham when Bishop Wilfrid visited Sussex in 681. Bosham church is famously depicted on the Bayeux Tapestry, in the scene showing Harold's embarkation for Normandy. By 1086 it had received considerable endowments, namely 65 hides at Bosham and 82 hides in other estates in Sussex and Hampshire, totalling 147 hides. Before 1066 the church and much of its lands were held by Edward the Confessor's clerk Osbern who, as a Norman, managed to retain them under King William. After becoming Bishop of Exeter (1072-1107), he attached his holdings at Bosham to the bishopric. In 1086 five clerks and a priest are mentioned, and c.1121 a college of six prebends was established by Bishop William Warlewast of Exeter (1107-37), who himself retained the position of Dean. It is possible that the college already existed in 1086, and was merely re-established or reformed c.1121. From the 12th century the parochial nave was served by a perpetual vicar. Successive Bishops of Exeter continued to hold Bosham until the Dissolution.

Bosham is essentially an Anglo-Saxon church with later medieval additions and modifications. The inserted chancel arch, which used to be assigned a pre-Conquest date, is now dated after c.1070 (Gem 1895, 35). The chancel was twice extended, the first extension being characterised by herringbone masonry typical of late 11thc. or early 12thc. work. The second extension, including the present E wall, belongs to the 13thc.

The corbel table of the W tower bears remarkable similarities to those of Chichester Cathedral, which can be dated c.1070-1125. At Bosham, the three-storeyed Anglo-Saxon tower survives to the level of its corbelled eaves. A new belfry stage was added to that after the Conquest, either c.1080-1100 or c.1125. The timbers of the spire were felled in the winter of 1405-06.

The pillar piscina cannot be in its original position as the aisles were not added until the 13th century. Presumably it was moved when a new piscina was introduced as part of the second chancel extension. Its simplicity could have been created at any time in the first third of the 12th century, but it was probably carved c.1100 for the newly extended chancel.

It is difficult to relate the five chevron voussoirs to the fabric of the church and they may have been brought to Bosham from elsewhere as there is no evidence that they were kept in the church before the 1960s. They appear to be among the earliest examples of chevron in the county and are technically related to the voussoirs of the S doorway of the SW tower, Chichester Cathedral, c.1125-1150.

Capitals on the scale of the fluted capital, carved on three faces, appear in a limited number of architectural contexts (eg: blind arcading), none of which occur in the 12thc. work at Bosham (chancel and tower, upper storey). The capital may have belonged to a piece of church furnishing or may have been brought to Bosham from elsewhere.

The font is typologically related to the group of square Sussex marble fonts, carved with shallow arcading and carried by columns, which are common in this region. The octagonal shape, however, is unique in Sussex.