The main church of Kotka is the Evangelical Lutheran Cathedral, built in 1898 of red brick neo-Gothic style designed by Josef Stenbeck. Inside are 1560 seats. Spacious building with a height of 54m, with magnificent stained-glass windows, a beautiful ornament on the columns and amazing carved wooden interior serves as a concert hall to listen to organ music.

The church organ, which has 44 registers made Marty Portanenom Baroque organ in the likeness of Freiberg Cathedral in Germany, was established in 1998. the hundredth anniversary of the church. Altar painting "The Adoration of the Magi", written by Pekka Halonen, depicts the infant Jesus.

The main church of Kotka belongs to the Diocese of Mikkeli. Visitors to offer guided tours.