The church was built in the 12th century, and its unusual east tower originally housed the chancel and altar in an apse at its base, with the nave entered through a south portal and lit only by a few small windows. This layout makes Ås highly unusual among Swedish parish churches, most of which place the tower to the west.
During the 1770s the nave was extended westward by around eight metres, and the building was reworked as a Neoclassical hall church, one of the earliest of its type on Öland. In 1820 further changes followed: the old chancel and apse in the tower were walled off to form a sacristy, and a combined altar-and-pulpit structure was installed against the new east wall, incorporating older carved elements. A lantern was added to the top of the tower the same year, giving it the silhouette still seen today.
Inside, a wooden barrel vault dates from the 1770s rebuilding. During a more recent interior renovation, stone side benches from the medieval church were discovered, a reminder of the building's much older origins beneath its Neoclassical appearance. The church also has a small west porch, and the surrounding churchyard is enclosed by a dry stone wall, with the manor lands of Ottenby pressing close on most sides.
Among the furnishings are sculptures of Moses with the tablets of the law and John the Baptist, a woven wall hanging with a landscape scene, and a model of a three-masted full-rigged ship dating from 1888, a common maritime votive tradition in Swedish coastal churches. The font was made locally in Grönhögen in 1938. The current organ, built in 1884 by Åkerman & Lund of Stockholm, replaced an earlier second-hand instrument that had originally come from the German Church in Karlskrona.
Of the old rectory only the barns to the south of the church remain, and a high wall built under Karl X separates the churchyard from the village of Näsby to the east. The tower's bells have on occasion been broadcast to ring in the New Year on Swedish television, according to local tradition.