The original church at Istorp was probably built during the medieval period, though little of that early structure survives today. A major rebuilding in 1734 replaced the south and east outer walls, and the church took on much of its present form during the first half of the nineteenth century. In 1804 the building was extended eastward and the chancel given its current five-sided shape, followed by the construction of the west tower in 1805. Further work in 1836 raised the outer walls and renewed the roof vaulting, while the tower was rebuilt in 1841 and topped with the lantern that still crowns it.
The church has a rectangular nave with a chancel that appears rounded from the outside, though it is technically five-sided. Walls are plastered white inside and out, pierced by arched window openings, and the interior is covered by a wooden barrel vault. Twentieth-century renovations, notably one led by architect Axel Forssén in 1925 and another under Kaj Christensen in 1945–46, altered doorways, flooring and the colour scheme of the pews, while a further interior restoration in 1990–91 introduced the blue and white tones seen today.
Among the furnishings, the pulpit on the north wall is thought to date from around 1700 and is attributed to the sculptor Gustav Kihlman, its brown-painted panels carved with figures of the four evangelists. The altarpiece, in a neoclassical style, was made in the 1820s by the joiner Petter Carlsson of Öxnevalla; the crucifix figure was added in 1946, and since 1969 it has been flanked by two wooden reliefs depicting the Nativity and Resurrection by Erik Nilsson of Harplinge.
The font dates from around 1915, made by the joiner Edvard Börjesson of Kulla, and was originally painted white before receiving its present grey-green marbled finish in 1925. Its accompanying font bowl is considerably older, dated to 1645 and said to have been donated by a local landowner. The church bells are said to date from 1707 and 1773, with one bell reportedly recast in 1786 by the Gothenburg bell-founder Jonas Wetterholtz.
North-west of the church stands a mortuary building originally constructed as a medieval bone-house in the 1400s, and nearby a former rectory dating from 1795, refaced in the early 1920s. A parish hall from 1927 stands beside the southern churchyard wall.