The plan of All Saints Church comprises a west tower with heavy buttresses and a broach spire, a three-bay nave with a tall aisle on the north side (described by one historian as "quite out of proportion to the rest of the building, particularly in height"), and a porch on the south wall, a chancel and a vestry.
 Although the north aisle of 1898 was flint-built with courses of red brick, the rest of the church's exterior was clad in cement at the same time.
 Before this, the outside walls had been entirely flint with stone dressings and sandstone quoins.
 Both sides of the nave are buttressed, as is the southwest corner of the tower.
 These buttresses may have been added in the 16th century.
 The roof of the tower, below the squat 19th-century spire, is of slate; the rest of the church has a tiled roof.
 The porch has a gabled roof above a 14th-century archway.
 The tower contains three bells.
 One is dated 1639, and another is known to have been repaired in 1724.
 The chancel roof is panelled, while the nave roof has vertical queen-post supports with ancient tie-beams.

The nave and chancel are separated by an ancient chancel arch which has recesses for a reredos on each side.
 These may be contemporary with the 12th-century structure.
 Above the chancel arch are the remains of a 13th-century wall painting showing Christ in Judgement.
 It has been dated to c. 1230, and depicts the ascension to Heaven of the dead and the weighing of their souls by Jesus Christ, who is flanked by the Virgin Mary and John the Baptist.
 The fresco was in fragmentary condition when it was discovered in the 1880s, and has been redrawn.
 Other paintings may have existed elsewhere on the walls, but none are visible now.

There are lancet windows in the north and south walls and on the tower, some with stone tracery (including the east window in the main body of the church).
 The chancel and nave windows are 14th-century and in the Decorated Gothic style common at the time, while the tower windows and bell-openings are smaller and in the Early English style popular in the 13th century, when the tower was built.
 The largest window, which sits under a hoodmould, is in the east end of the chancel; it is a three-light lancet with prominent tracery in the curvilinear/reticulated style.
 The window dates from the 14th century, which may make it the same age as a small window next to the porch, which has twin lights with foliated heads set below a quatrefoil in an ogive arch.
 Both windows also have scrollwork drip-moulds.
 Most other windows are plain trefoil-headed single lancets.

The blocked doorway in the modern north aisle is the oldest surviving part of the church.
 Its lintel is 10 inches (25 cm) thick and sits below 11 voussoirs, each about 8 inches (20 cm) across.
 Below the lintel, the former opening is 6.8 feet (2.1 m) high and 2.75 feet (0.84 m) wide; gradual settling into the ground has masked its original 7.5-foot (2.3 m) height.
 The jambs are made up of five stones of equal height, but the uppermost is wider because it served as an impost.
 Inside the church, the jambs and arch are visible, but there is no lintel.

The wall of the chancel retains a trefoil-arched piscina added during the 14th-century restoration work.
 The font—a "rather florid circular" example—dates from 1864, and the church possesses Eucharistic objects dating from the 16th and 17th centuries, such as a chalice of 1568 and a paten dating from 1666.
 The west wall has a wide range of old carved prayer and commandment boards, which are a common feature of Sussex churches.
 Ancient examples of graffiti, consisting of etched crosses and dates, also survives inside; such "curious carvings" are also common in Sussex.
The plan of All Saints Church comprises a west tower with heavy buttresses and a broach spire, a three-bay nave with a tall aisle on the north side (described by one historian as "quite out of proportion to the rest of the building, particularly in height"), and a porch on the south wall, a chancel and a vestry.  Although the north aisle of 1898 was flint-built with courses of red brick, the rest of the church's exterior was clad in cement at the same time.  Before this, the outside walls had been entirely flint with stone dressings and sandstone quoins.  Both sides of the nave are buttressed, as is the southwest corner of the tower.  These buttresses may have been added in the 16th century.  The roof of the tower, below the squat 19th-century spire, is of slate; the rest of the church has a tiled roof.  The porch has a gabled roof above a 14th-century archway.  The tower contains three bells.  One is dated 1639, and another is known to have been repaired in 1724.  The chancel roof is panelled, while the nave roof has vertical queen-post supports with ancient tie-beams.
The nave and chancel are separated by an ancient chancel arch which has recesses for a reredos on each side.  These may be contemporary with the 12th-century structure.  Above the chancel arch are the remains of a 13th-century wall painting showing Christ in Judgement.  It has been dated to c. 1230, and depicts the ascension to Heaven of the dead and the weighing of their souls by Jesus Christ, who is flanked by the Virgin Mary and John the Baptist.  The fresco was in fragmentary condition when it was discovered in the 1880s, and has been redrawn.  Other paintings may have existed elsewhere on the walls, but none are visible now.
There are lancet windows in the north and south walls and on the tower, some with stone tracery (including the east window in the main body of the church).  The chancel and nave windows are 14th-century and in the Decorated Gothic style common at the time, while the tower windows and bell-openings are smaller and in the Early English style popular in the 13th century, when the tower was built.  The largest window, which sits under a hoodmould, is in the east end of the chancel; it is a three-light lancet with prominent tracery in the curvilinear/reticulated style.  The window dates from the 14th century, which may make it the same age as a small window next to the porch, which has twin lights with foliated heads set below a quatrefoil in an ogive arch.  Both windows also have scrollwork drip-moulds.  Most other windows are plain trefoil-headed single lancets.
The blocked doorway in the modern north aisle is the oldest surviving part of the church.  Its lintel is 10 inches (25 cm) thick and sits below 11 voussoirs, each about 8 inches (20 cm) across.  Below the lintel, the former opening is 6.8 feet (2.1 m) high and 2.75 feet (0.84 m) wide; gradual settling into the ground has masked its original 7.5-foot (2.3 m) height.  The jambs are made up of five stones of equal height, but the uppermost is wider because it served as an impost.  Inside the church, the jambs and arch are visible, but there is no lintel.
The wall of the chancel retains a trefoil-arched piscina added during the 14th-century restoration work.  The font—a "rather florid circular" example—dates from 1864, and the church possesses Eucharistic objects dating from the 16th and 17th centuries, such as a chalice of 1568 and a paten dating from 1666.  The west wall has a wide range of old carved prayer and commandment boards, which are a common feature of Sussex churches.  Ancient examples of graffiti, consisting of etched crosses and dates, also survives inside; such "curious carvings" are also common in Sussex.
All Saints Church, Patcham