The present church was completed in 1754, replacing a decayed medieval timber church that had stood on a headland at Ekeby, some way from the current site. By the late 1600s that older building was in poor repair, and after long discussion among parishioners about a more convenient location, landowners at Flarka offered ground for a new church nearer the growing settlement of Horn. The new building was consecrated on Queen Lovisa's name day and became known as Lovisa kyrka in Horn, though it is now generally called Horns kyrka.
The church was designed and built by Petter Frimodig, a master builder from Linköping known for a distinctive style of tall, slender spires, seen also at Ingatorps kyrka in Småland. Horns kyrka is considered one of the best-preserved examples of his work. The building has a rectangular nave with a straight-ended chancel, a sacristy to the north-east and a west tower beneath a steep hipped roof, originally covered in wooden shingles. The interior features a high barrel vault typical of the mid-18th-century Rococo period.
When the old church was demolished, some materials were reused in the new building, including painted timbers now built into the roof structure. Dendrochronological analysis has dated these timbers to the late 14th century, and older written sources suggest the fragmentary painted scenes and inscriptions on them date from 1404, though the paintings themselves are now very worn and only partially legible.
Inside, the church retains much of its original fixed furnishings, including a pulpit and altarpiece attributed to the sculptor and painter Jonas Berggren, trained in Kalmar and Stockholm, who worked in several churches within the diocese. Funeral hatchments (heraldic memorial panels) for the Scheiding and Drake noble families can also be seen, along with some furnishings said to date from the medieval period. The site of the old church at Ekeby survives only as a disused churchyard and building foundation, with a former curate's residence nearby.
The church has had several organs over the centuries; an early instrument was sold to Bjälbo kyrka in 1759, and a new organ was built in 1767 by the Småland organ builder Lars Wahlberg. Its decorative case survives and was reused in a later mechanical organ built in 1962.