Kefeli Mosque (or Kefevi Mosque) is situated on the sixth hill, in the northwestern part of Constantinople, a short distance from the Monastery of Chora and the ruins of Odalar Mosque and Boğdan Palace. In the Early Ottoman era, it was a church dedicated to St. Nicholas that was used jointly by Dominicans and Armenians.

The Byzantine identity of Kefeli Mosque is uncertain. It has been suggested that it is the Monastery of Manuel, founded by a general general active during the reign of Theophilos (821-842), since his burial was in the vicinity of the Cistern of Aspar. However this is unlikely since its multifaceted apse and the banded masonry are characteristic of Late Byzantine buildings in Constantinople. In addition, there were several monasteries nearby including some extant Byzantine churches with uncertain identities.  Its identification is also problematic since its northward orientation makes it highly unlikely that the structure was built as a church. It is more likely that it was originally a refectory of a monastery.
It was given to Christians from the Genoese colony of Caffa (Turkish Kefe, Greek Theodosia) in the Crimea after its conquest in 1475. It was then dedicated as the Church of St. Nicholas and used jointly by Dominicans and Armenians, who had separate altars. It was converted into a mosque by Recep Pasha around 1630. In the course of conversion minor interventions such as the walling up of some windows were undertaken. The building was surveyed the building in the 1960s, during which evidence of lateral aisles was discovered. In the 1970s the building was restored during which the minaret was repaired.

As it survives today Kefeli Mosque is a rectangular apsed hall, measuring around 22 x 7 meters. Its masonry consists of alternating bands of brick and ashlar. The spacing of the arches in the main nave is irregular. The apse has four absidioles inscribed in the thickness of the wall, but there were no side apses. A wooden roof currently covers the nave, and the absence of any kind of springing for a vault indicates this was also the original means of roofing. The exterior is marked by a series of heavy pilasters that ends below the level of the clerestory windows, supporting the roof of the side aisles, which most likely was also wooden. It also had a cistern, measuring around 7x5 meters with a rectangular plan. The cistern had a single row of 3 columns, with Ionic capitals decorated with crosses.