The oldest surviving parts of the church, including its sturdy tower and the lower portion of the nave, date back to the 1200s, when a Romanesque church with an unusually large chancel stood here, entered originally through a doorway in the south wall. At some point during the late medieval period the building suffered a fire, and the brick vaulting of the nave and chancel is thought to have collapsed as a result, probably in the 1400s. A porch was added in the same century.
By the late 1700s the medieval church was considered too small for the growing congregation, prompting a radical rebuilding between 1779 and 1782. The old chancel, sacristy and porch were demolished, and the nave was extended to more than double its former length. A new sacristy was built to the north, fresh entrances were opened in the west and south walls, and the tower gained the lantern-topped cupola that still crowns it today, giving the church much of its present external appearance.
Despite the extensive rebuilding, the church retains a notable collection of medieval fittings. Among the woodcarvings are a thirteenth-century figure of St Olof and a late fifteenth-century figure of John the Baptist, both said to be of high quality. A triumphal crucifix of around 1200, mounted on a later cross, decorates the south wall, while a late medieval processional cross hangs on the north wall. The stone font in the chancel is also thought to date from around 1200, and above it hangs a Marian cabinet shrine of about 1500 depicting a gold-crowned Madonna and Child.
The church organ has its own layered history: an instrument with ten stops was built in 1850 by Johan Lund of Stockholm, and in 1938 a new organ with thirteen stops was installed by E. A. Setterquist & Son of Örebro, reusing the 1850 case and around eight of the earlier pipe stops.
A parish hall known as Gåsinge Tingshus stands beside the church and has historically been used, alongside the church itself, for christenings, weddings and funerals, including civil funeral services.