Ilmer is a picturesque hamlet of a few houses clustered around the church, with views of the Chilterns and Bledlow Great Wood to the S. It lies in rolling, wooded pasture land in the west of south Buckinghamshire, 6 miles SW of Aylesbury and a mile from the Oxfordshire border.

The small, simple church has a square-ended chancel and a nave with a N porch and a timber bell-turret towards the west end, with a shingled needle broach spire. Construction is of coursed stone rubble and largely of the 13thc, although there is a blocked 12thc S doorway and some of the windows and the piscina have ogee heads indicating a 14thc campaign. The jambs of the easternmost S nave window continue to the ground, indicating that it was formerly the entrance to a chapel or transept, blocked in its lower part in the 18thc-19thc. The interior of the church is plain with no chancel arch but an attractive 15thc screen with timber tracery. The church was in a dilapidated state by 1860, and in that year work began on its restoration, which involved the rebuilding of the chancel and the restoration of the nave. The spire was reshingled in 1978-79.

Godwine, a man of Earl Leofwine, held the manor of Ilmer before the Conquest. In 1086 it was held by Robert from Odo, Bishop of Bayeux, and consisted of 4 hides with meadow for 5 plough-teams and a mill. By the 12thc the manor was in the possession of Robert de Romenel, and in 1336 it was held by John de Moleyns, who was granted a licence to enclose the woods and park in that year. Sir Robert Dormer held the manor in 1538, and it remained in his family until 1858.

The church was given to the Benedictine nuns of Studley priory (Oxfordshire) before 1205 by Thomas, son of Bernard. It now belongs to the Risborough Team ministry which consists of Princes Risborough with Ilmer; Monks Risborough with Owlswick; Lacey Green with Speen and Loosely Row; and Bledlow with Saunderton and Horsenden.

The doorway was measured to ground level, but was clearly taller originally.