The original stone church at Medelplana, whose earliest recorded name was "Medel Up I Landom", was built around 1150. Its dedication to Saint Helena is echoed nearby by a spring bearing her name near Bosgården, with another spring in the area named after Saint Apollonia.
The medieval building had a rectangular nave separated by a triumphal arch from a square chancel with a straight east wall, a porch on the south-west side serving as the main entrance, and a sacristy to the north-east beside the Gyllengrip family burial chapel. The interior was covered with whitewashed medieval stone vaulting.
A 1763 plan to rebuild the church as a cruciform structure was only partly realised, with just an arch cut through to the tower. By the early nineteenth century the building had become too small for its congregation, prompting a major rebuilding in 1823–1824 that gave the church its present form: broad cross-arms were added to the north and south, forming a new nave running north–south. The tower base and the medieval east and west gables survive from the earlier building, still visible today, particularly on the west wall. A medieval lychgate at the northern entrance to the churchyard also remains, with an old poor box mounted nearby; a further lychgate was added at the south side in 1927.
In 1902 the church underwent a thorough restoration, during which a five-sided sacristy was built onto the north gable, replacing the tower's ground floor, which had previously served that purpose. The tower was given its tall, copper-clad spire, and new pews were introduced. A further restoration followed in 1926–1927, when several older furnishings were renovated and reinstalled, and a more extensive restoration took place in 1964–1965, when most of the chancel pews were removed (one remains beside the pulpit), a bridal chamber was created at the west end, and epitaphs and portrait memorials were rearranged to give the interior a more unified appearance.
Among the church's furnishings is an altarpiece depicting the institution of the Eucharist, painted around 1660 by Johan Aureller the Elder. The current pulpit, in a grey-green marbled Renaissance style, dates from 1902 and is the fourth to have stood in the church; the sandstone font and its silver dish were made in 1948. The organ was designed in 1902 by Carl Axel Härngren of Lidköping and later restored. According to local tradition, Bishop Bengt donated two bells to the church in the twelfth century, though the bells now hanging in the tower appear considerably younger: the larger, roughly cast and uninscribed, resembles seventeenth-century work, while the smaller carries a late-medieval inscription naming a priest called Olaus as its maker.