The Concert Organ in Hallgrímskirkja was built by the Johannes Klais organ factory in Bonn, Germany and is the largest musical instrument in Iceland. It was inaugurated on December 13th 1992. The organ has 4 keyboards and pedals, 72 voices and 5275 pipes. The organ is 15 meters high, weighs about 25 tons, and the largest pipes are about 10 meters high. The purchase of the organ was largely financed by donations. People were invited to buy the pipes, and it is still possible to buy a gift certificate in the church's store, which certifies that the person is the owner of a particular pipe in the organ.
The church organ is used during church services, and has received general recognition as an excellent concert instrument. The introduction of the portable organ console has significantly increased the organ's range of performance configurations. It is praised among organists around the world for its quality, varied voice selection and organic integration into the space.
The Choir Organ, is located in the Choir at the north end of the church. It is a 10-voice choir organ built by Th. Frobenius and Sønner Orgelbyggeri A/S in Lyngby, Denmark and was inaugurated in December 1985. It has ten mechanical voices with a svelte on both playing boards. It replaced a 14-voice Czech Rieger-Kloss organ that had originally been installed in the chapel in 1956 and been moved to the south wing of the tower when the chapel was ordained there in 1974. When the church was ordained in October 1986, it was moved where it is now and has served the church ever since. It was the sole organ of the church for the first six years.