Unlike most churches in the region, which were substantially altered during and after the Reformation to reflect the manor-house-influenced tastes of those eras, Nykyrka kyrka largely preserves the appearance of an earlier age of church building. This makes it one of the more architecturally distinctive churches in the diocese of Strängnäs.
The church was built of grey stone in the second half of the twelfth century as an apse church, comprising a rectangular nave, a narrower and longer chancel, and an apse to the east. The apse was demolished in the 1760s when an octagonal burial chapel was added; the sacristy dates from 1767, contemporary with that chapel.
The building had a troubled later history: it fell into serious disrepair and stood unused from 1814, when it was taken out of service, until 1926, when restoration work began. The church was reconsecrated in 1929 and is now regarded as one of the most ancient-looking churches in the diocese. The wooden bell tower recalls the type used in the church's earliest period, although its timber has been renewed more than once over the centuries.
Among the furnishings, the font and a gravestone are said to date from the church's earliest period. The altarpiece, by Ernst Söderberg, was installed in 1943. A runestone (Sö 46) stands near the church.
A harmonium served the church before 1954, when the present mechanical organ was built by Grönlunds Orgelbyggeri of Gammelstad.