The present church was built partly at the initiative of Knut Persson, a forceful local farmers' estate parliamentarian known locally as the 'King of Mjällby'. It replaced a Romanesque stone and brick church dating from the 1100s, which itself is said to have stood on the site of an earlier wooden mission-era church, reputedly built at a pagan place of sacrifice. Historical sources note that during parts of the Middle Ages the Archbishop of Lund held economic interests in the village of Mjällby.
During the medieval period the earlier church was known for a large triumphal crucifix, which today is held at the Blekinge Museum in Karlskrona rather than in the church itself.
The surviving altarpiece, dated 1621, was donated to the church by Tage Thott, a Danish governor based at Sölvesborg Castle, and his name remains inscribed on it along with that of King Christian IV. The altar's antemensale, font and pulpit are said to date from the same period, giving the interior a notably cohesive early seventeenth-century character.
A distinctive wall painting depicting the four evangelists surrounds the altarpiece on the chancel wall; it was painted around 1835 by Carl Strömberg and remains one of the more memorable decorative features for visitors.
The church's tower roof, covered with some 22,000 oak shingles, was relaid in 2007 as part of a wider programme of restoration, alongside interior work in 2006 and facade repairs to the nave in 2008. The church has had at least two organs: an 1885 instrument by Åkerman & Lund, later enlarged, and the current mechanical organ built in 1972 by Mårtenssons orgelfabrik, which retains the earlier organ's 1885 façade.