The construction of Karjalohja church, which was designed by architect C. L. Engel’s student architect Jean Wiik, was finished in 1860. The church is built of grey stone and it has a bell tower on the western end of the church. Karjalohja church is situated in Karjalohja church village on top of an esker with a view to lake Puujärvi and lake Lohjanjärvi. The church has 350 seats.
Karjalohja church was used actively for 110 years until it was struck by lightning on the 21st of September in 1970. The church caught fire and eventually only the stone walls were left standing. People were able to save some pieces of the interior like the altar painting, a chandelier, a baptismal font, some smaller paintings and a candle tree designed by Maija af Ursin and made by local smith Sillanpää. The altar painting was painted by Alexandra Ståltin in 1881. The church ruin was left unprotected and exposed to harsh weather conditions for 20 years.
In 1987 the Finnish Heritage Agency demanded that the ruin had to be protected in order to stop crumbling and decay. In 1989 people started different charity events in order to raise funds to build a new roof for Karjalohja church. The new roof was finished in 1990 thus saving the church which already was on the verge of collapsing. The bishop of Helsinki opened the church for use on the 9th of June in 1991.
More renovating was carried out in the 1990s using funds raised by charities. A new bell tower, which was constructed in three parts, was finished in 1995. Between the years 1970 and 1977 the parish of Karjalohja borrowed church bells from a former village church Pitäjänmäki.