The oldest parts of Ova kyrka, principally the nave, survive from the medieval stone church built in the twelfth century. The building's fortunes became linked to Mariedal Castle after Magnus Gabriel De la Gardie began constructing the castle in 1666; he initiated repairs to the church in 1668. The church was later extended westwards in 1722, when the present three-sided chancel was added.
The flat wooden ceiling is decorated with eighteenth-century paintings depicting the Creation, the Fall, the expulsion from Paradise, the Crucifixion and the Last Judgement. These were painted in 1742 by Johan Liedholm, associated with the so-called younger Läckö school of decorative painters, who was based in Skara and Mariestad; he is also credited with the twelve painted apostle panels on the gallery front.
The altarpiece, showing the Last Supper, dates from the De la Gardie period and is thought to be the work of the French artist Nicolas Vallari, who was in the family's service; the pulpit, from around the same time, is also attributed to him, though this is not certain. On either side of the church can be seen the coats of arms of Magnus Gabriel De la Gardie and his wife Maria Euphrosyne.
Among the church's furnishings is a font dating from the twelfth century, one of the oldest surviving objects, though its base was renewed and it was repositioned in the chancel in 1913. Several finely carved medieval grave slabs (liljestenar), once set into the floor, are now displayed in the porch and leaning against the church's north wall.
Two chandeliers hang in the church. The finer of the two is topped with a double eagle and bears a Russian inscription; tradition holds it was given to the church by a Countess De la Gardie in the early 1700s, and may have been war booty taken during Jacob De la Gardie's campaign that captured Moscow in 1610, though this account cannot be verified. The second chandelier was donated by Sophie Sparre in the early twentieth century.
The church is built of dressed sandstone with rendered walls, a three-sided east end, a sacristy to the north and a porch to the west.