Fethiye Mosque is located near Çarsamba neighborhood of Fatih district. It was originally a Byzantine church, built on the fifth hill of Constantinople (modern Istanbul) in the beginning of 12th century and then rebuilt in the 13th century by Michael Glabas Ducas Tarchaniotes, nephew of the emperor Michael VIII Palaeologos. Glabas was buried in the parakkleison (side corridor) dedicated to Christ, which was added to the building in 1315 by his wife Maria in the memory of her husband. After her death, Maria was also buried in this funerary chapel.

After the conquest of the city in 1453, the church was used as a nunnery and then it became the see of Christian Orthodox Patriarchate from 1455 until 1587. In 1590, Pammakaristos church was converted into a mosque with the name Fethiye (conqueror), in order to commemorate the conquest of Georgia and Azerbaijan by the Ottomans under the reign of sultan Murad III during the Iranian war. A part of the apse was removed and a niche (mihrab) was built showing the direction of Mecca. A minaret and medresse were also added.

During the Republic, frescoes and mosaics inside were uncovered in 1955 and it became a museum. The arch built by the Ottomans was replaced by columns as the original. In the 1960's the mosque was once again opened for worship which is still in use, while the parakkleison section of the building remained as a museum.

The south chapel (parakkleison) represents a cross-shaped plan with a dome of 2.30 meters on the naos, a gallery and a narthex. The external walls are typical of the Late Byzantine architecture, made of stone and bricks. In the southern side there is an inscription stating that it was built by Glabas, while on a marble slab there is a poem.

At the entrance, there is a well preserved frescoe on the wall with "three wise men", and some fragments of other frescoes. Inside the dome and the interior wals of the parekkleison are covered with mosaics from the 14th century. The dome is decorated with Christ Pantokrator and the Twelve Prophets. In the apsis, there are figures of Christ with Virgin Mary and John the Baptist forming the Deesis, and archangels watching them. In the vaults and arches, there are scenes of the Baptism, and of several saints and monks of the church.

The museum is open between 09:30 - 16:30 except on Wednesdays.