[3] The original centre of population was a small cluster of houses further south, surrounded by fields and next to a creek between Chichester and Langstone Harbours.

[3] Nothing remains from the original nave and chancel to the east; based on measurements from the present church, the Victoria County History states they may have been 13.5 feet (4.1 m) wide.

[3][7] Dating from this period are a three-bay nave with north and south aisles and arcades, and the upper storey of the tower[3] (not yet topped by its present shingled spire).

[1][2] The significant enlargement of the church may have been prompted by the growth at that time of Emsworth, always the main settlement in the parish, which became a port in the 13th century.

[8] Also in the late 13th or early 14th century,[note 2] the chancel floor was laid with glazed encaustic tiles similar to those at nearby Titchfield Abbey.

[9] People in Emsworth had to travel the 2 miles (3.2 km)[3] to Warblington to worship until 1789–90, when a chapel of ease was built in the town's market place.

Warblington was a popular site for this activity because of its "lonely but well-filled churchyard",[12] isolated in a rural area and well screened by yew trees.

In 1829–30 the church authorities employed local builders Benjamin Chase and James Cullis to build huts for grave-watchers at the northwest and southeast corners of the churchyard.

[14] A programme of conservation and restoration work lasting several months took place to clean soot and smoke particles from the walls, ceiling beams, floor tiles, windows, arcade pillars and memorials using materials such as limewash and latex.

The uppermost stage, topped with a shingled spire added during the Victorian era, contains one bell and has paired lancet windows.

[9] The nave is "comparatively wide"[2] and has three bays, each with a lancet window which on the outside extends well above the low, steeply sloping roofline, forming a series of gabled dormer windows—an appearance which contributes to the many-angled, "highly picturesque outline".

The "beautiful" south arcade[1][8] has octagonal piers and shafts of Purbeck Marble with richly detailed foliate capitals, similar to contemporary work at nearby Chichester Cathedral[8][9] and Boxgrove Priory church.

[1][9] The "fine medieval porch"[17] on the north side has woodwork of high quality in the arch and gable, dating from either the 14th[9] or the 15th century,[1] including bargeboards with fretwork tracery, and timber-framed stone inner walls.

[20] On the walls are several cartouches of the late 18th and early 19th centuries, at least one signed by J. Morey, a member of a family of sculptors who is buried in the churchyard.

[20] There is also a monumental brass of the late 16th century, depicting Raffe Smalpage (Henry Wriothesley, 2nd Earl of Southampton's personal chaplain) kneeling at a desk.

They are of galleted flint with red-brick dressings and quoins, hipped roofs laid with slate tiles, and pointed arched entrances and windows with shutters.