The church's tower predates the rest of the building and is said to have origins as a defensive structure, from a period when the old national border ran along the nearby Stångån river. It received its present onion-shaped roof and closed lantern in 1791, giving it a notably shorter spire than it originally had.
Among the church's oldest furnishings is a sandstone font, carved in the late 12th or early 13th century and decorated with a simplified ring-chain pattern typical of fonts from southern Västergötland. In 1693, parishes across Sweden marked the centenary of the Uppsala Synod's decision with a commemorative document; only two of these are known to survive today, and one hangs in Håcksvik's church.
The church contains two altarpieces. A neoclassical altarpiece, matching the rest of the interior, serves at the altar, while an older altar screen was brought back into the church in 1927 and now stands in the centre of the nave, with the medieval font placed in front of it. The altarpiece and pulpit are early works by the sculptor Johannes Andersson of Mjöbäck, dating from 1831.
Three coats of arms hang on the walls, belonging to the Hultengren, Silfersverd and Kuylenstierna families, offering a glimpse of the church's connections to local landed gentry.
The church's larger bell dates from the early medieval period and bears no inscription, while the smaller bell was cast in 1885 by C.A. Norling of Jönköping. The organ, built in 1876 by Salomon Molander, retains its original facade despite later rebuilding and renovation work in the 20th century.