The Domesday Book compiled in 1086 includes two churches entered under the Manor of Warblington (which at the time incorporated the Manor of Westbourne) It is possible that one of these either Saxon or Norman foundations was in Westbourne – potential evidence for this might be traced to claims made during the church's restoration in 1865, where "large square bases of early Norman pillars" were allegedly seen on the site where the present pillars stand.

The current church that stands today consists of structures dating back to the early 13th century and other appendages and renovations since then.

In the late 14th century, the rector and 6th Earl of Arundel carried out considerable alterations.

In 1876, the organ chamber was built and new choir seating was installed, and Philip Mainwaring Johnston undertook further work in 1932–33.

[2] In 1892, a tin church was built in the nearby village of Woodmancote and was incorporated into the benefice of Westbourne.

Its activities include Sunday school, a junior section to the choir and other youth involvement.

In 1862, a one manual organ constructed by J. W. Walker & Sons Ltd was installed - it was enlarged fourteen years later to include a second manual (Swell division) In 1890, W. J. Haywood of London carried out additions to the organ, including an 8' reed to the swell and 16' Open Wood to the pedals.