St:John's church was built on the Punavuori hill, on the outskirts of the city at that time. The church was completed in 1891. It was designed by the Stockholm-based architect Adolf Emil Melander. Initially, the chuch was called the New Church. The need for a new church arose because the inhabitants of Helsinki could no longer fit into the Old Church and St. Nicholas' Church, now known as the Cathedral. The New Church was built on the site of a midsummer bonfire and was dedicated to St. John the Baptist.
The Neo-Gothic St:John's church has the shape of a three-aisled basilica. It is Finland's largest stone church, originally with 3000 seats. Several rows of benches have since been removed to make the church hall more functional. Currently, there are just over 2200 seats. The church towers are 74.22 meters tall. The church bells, which play the first three notes of the Te Deum hymn (C sharp, E, and F sharp), were installed in 1932.
The church was last renovated before its centenary celebrations in 1991. At the same time, part of the church basement was converted into a crypt.