One of the most important examples of Constantinople's Palaiologan architecture, the mosque contains the largest quantity of Byzantine mosaics in Istanbul after the Hagia Sophia and The Chora.

[4] Following the conquest of Constantinople in 1453, the seat of the Greek Orthodox Patriarchate was first moved from Hagia Sophia to the Church of the Holy Apostles.

[5] Five years later, the Ottoman Sultan Murad III converted the church into a mosque and renamed it in honor of his conquest (fetih) of Georgia and Azerbaijan, hence the name Fethiye Camii.

In this technique, alternate courses of brick are mounted behind the line of the wall, and are plunged in a mortar's bed, which can still be seen in the cistern underneath and in the church.

It has the typical cross-in-square plan with five domes, but the proportion between vertical and horizontal dimensions is much more attenuated than usual (although not so big as in the contemporary Byzantine churches built in the Balkans).

Although the inner colored marble revetment largely disappeared, the shrine still contains the restored remains of a number of mosaic panels, which, while not as varied and well-preserved as those of the Chora Church, serve as another resource for understanding late Byzantine art.

A representation of the Pantocrator, surrounded by the prophets of the Old Testament (Moses, Jeremiah, Zephaniah, Micah, Joel, Zechariah, Obadiah, Habakkuk, Jonah, Malachi, Ezekiel, and Isaiah) fills the main dome.