The place name Alseda was recorded in 1290 as Alsidium, thought to derive from the Latin-influenced local words for alder tree and marshland, hinting at a settlement much older than the present church.
The building replaces an earlier stone church demolished in 1774, whose oldest parts are believed to date from the 12th century. Little else is known about that earlier structure. Its successor was built in a restrained Gustavian style, nearly 50 metres long, and is dominated by a robust west tower topped with an elegant curved spire, its outline broken by a white-painted band bearing clock faces. The semicircular chancel faces east in the traditional manner, with a sacristy adjoining to the north.
Construction was driven forward by successive vicars with direct royal and court connections, which is said to have smoothed the design process. The church was consecrated in September 1788, and the vicar most closely associated with completing its decoration was afterwards made a provost in recognition of his efforts on the parish's behalf.
Inside, the wide nave is covered by a light timber barrel vault, decorated in grey and white in a classical idiom with pilasters and ornamental symbols, work carried out in 1917. Furnishings include an altarpiece of Christ carrying the cross, an older 1788 altarpiece depicting the crucifixion on the south wall, a rounded pulpit with sounding board, and a carved triumphal crucifix believed to date from around 1500. The current organ, built in 1981, retains a case from an earlier 19th-century instrument.
In the south-east corner of the churchyard stands a building with medieval origins, thought to date from the early 12th century, later used as a tithe barn. Since 1989 its upper floor has served as a small summer chapel, furnished with a stone altar said to contain a relic recess possibly originating from the parish's very first church, along with a 17th-century font bowl and a crucifix from Oberammergau.