Nr. Onsild Church consists of a Romanesque choir and nave as well as a late Gothic tower in the west. The Romanesque building is built of granite blocks on a sloping plinth.
Large parts of the outer walls have been converted in recent times, with the exception of the north side and the bricked-up women's door. The church that stands today is the third on the site and smaller than the previous one. During the restoration in 1982, the choir was supported with a concrete mass to prevent further slipping.
The nave has a flat ceiling, while in the Gothic period a cross vault has been built-in. The tower, made of recycled squares and monk stones, has had an open pointed arch on the west side, which was bricked up in 1898. The same year the porch was demolished and only then was there an entrance to the church through the tower. The upper parts of the tower were rebuilt with bricks in the 1700s and bear the inscriptions MK and AMW, (Morten Kirketerp and Anne Marie Wedege 1740), the names of the church's patron and wife.
In the chancel arch is a beautiful chalk-painted vine decoration from around 1600. The decoration on the south side, however, is older, as it bears the inscription: "In the year of our Lord 1574 this picture was renewed". The altarpiece is from 1663 with a contemporary altar table front, while the altarpiece itself is a curious reproduction of Leonardo de Vinci's The Last Supper from 1850, as the disciple John, the disciple Jesus loved most, looks as if he has been beheaded. Above the altarpiece, the same initials can be seen on the church's patron as on the tower. Next to the church is the old church barn/tithe barn, which now houses gravedigging facilities.