A stone church at Kärna is thought to date from the 1100s, and tradition holds it was built around 1137 by King Sverker the Elder, at the same time as the nearby Kaga church. The original building had a short nave and a narrower chancel with an apse, likely lit by small, high windows in the Romanesque manner. Fragments of early painted ceiling boards were reportedly found when a stone vault was demolished in the eighteenth century.
Over the following centuries the church was altered repeatedly: the apse was removed and the chancel rebuilt with a straight east end, probably in the early 1300s; a vaulted sacristy and a porch were added in the 1400s; and the nave and chancel were given stone vaults decorated with medieval wall paintings. In 1567, during the Nordic Seven Years' War, Danish troops under Daniel Rantzau raided Östergötland and damaged the church, requiring further repairs. A tower was finally added in 1750, using stone for the lower section and red-painted timber above.
The church took its present cruciform shape after a major rebuilding completed in 1834, when the old church was retained as transepts and a new, broader nave and tower were added, designed with round-arched windows and an unusual octagonal glass lantern over the crossing. Much of this new interior was destroyed in a serious fire on New Year's Day 1893, which is recorded in contemporary newspaper reports. The rebuilding that followed introduced the barrel-vaulted, Neo-Classical-influenced interior visible today, with a panelled wooden ceiling and dark-stained woodwork.
Above the altar hangs a painting of the Ascension by the Linköping artist Johan Krouthén, made after the fire; a Neo-Baroque pulpit stands to one side. Older treasures said to survive from the medieval and early modern church include a communion chalice possibly made in Vadstena around 1500, later remodelled by silversmith Nils Dahl, and a wafer box attributed to the seventeenth-century silversmith Nils Nilsson Behm. The church's largest bell was recast in 1732, while the smallest dates from 1698.
A runestone stands in the churchyard, and an eighteenth-century description records its inscription as commemorating a father named Vaste, said to have been of foreign origin. The church's pipe organ, built up from an 1894 instrument by Åkerman & Lund with later work by Olof Hammarberg, was reported out of use in 2007; a separate chancel organ was installed in 2014.