The church's oldest parts probably date from the 1200s, though some accounts suggest building may have begun as early as the 1100s. It stands beside an Iron Age burial ground, pointing to more than a thousand years of settlement on the site. Norse-Icelandic sources claim that Bohuslän was Christianised as early as the late 900s under Olav Trygvasson, though no churches or Christian monuments survive from that early period, so the claim remains unverified locally.
Björlanda kyrka is considered a medieval Mary church, a status suggested by its unusually high walls. A note in Bishop Eysteinn's land register from the 1300s records the church's consecration day as 15 July, although the year of consecration itself is not known.
The tower-less building has thick whitewashed stone walls and a three-sided chancel the same width as the nave, with a porch at the west gable and a sacristy to the north of the chancel. It has been altered and restored several times: windows were added in the 1600s, a thorough rebuilding took place in 1734 (when the medieval chancel was demolished), and ceiling paintings by Lars Holm were added in 1740, though these no longer survive. A restoration in 1936 uncovered medieval mural fragments on the north wall, showing horsemen within circular medallions, thought to date from the 1300s. A freestanding bell tower stands on the south side of the churchyard, which was extended in 1913–1914 and enclosed by a stone wall with three lychgates built in 1738.
Among the church's furnishings is a well-preserved medieval font carved from soapstone by a master named Thorkillus, decorated with spiralling acanthus and a crowned, bearded head. The altar may date from the 1600s, and the pulpit is a Baroque work. Most of an older 16th-century altar cabinet is now kept at the Gothenburg City Museum, with only fragments remaining in the church itself. A 13th-century incense censer and a 19th-century votive ship are also among the church's older objects. In 1954, a ceiling painting by Kristian Lundstedt was added, moving from light above the gallery to darkness above the nave and back to light above the chancel, with the darker passage illustrating scenes from the Second World War.