In the year 1647 the Chapter accorded the parish of Marttila permission to build the chapel of Ylistaro (in other words Koski). The chapel was built in the same year. Before that the hours of devotion had been held in the manor of Koski. Already in the 1650’s the name Ylistaro was rejected and Koski became the only name according to the manor of Koski.

Since the dependent parish was built, there has also been a graveyard around the church. In the year 1652 the Chapter ordered the following: burial in the graveyard was free of charge, but inside the church it cost 1 taler per adult and 16 öre per child. Since 1798 it was forbidden to bury anyone inside the church anymore. The gentry of the manor did not agree to be buried outside, so the widow of Armfelt decided to build a tomb next to the bell tower. The year was 1819. When the ownership of the manor changed, the tomb was not used for many years until it was changed into a mortuary at the end of the century. During the entire chapel era the church was located in the same place where the graveyard of the parish is nowadays. All in all, four different church buildings have been located there: the first one was built in 1647, the second in 1652, the third 1679 and the fourth 1817.

The first two churches were very short-lived and very little information has been found about them. The third church was a cruciform church and the most important renovation of that time was the bell tower which was built in 1777. Like its predecessor, the bell tower became located at the western end of the church where it still is.

Renovation of the church became timely again in 1817 and that is when the new cruciform church was built a bit further from the bell tower.