The construction and naming of the monument is attributed to the Minister of Finance of Sultan Ibrahim Efendi, as the title of defterdar was held by senior financial officials of the Ottoman administration. Chronologically, it probably dates back to the same period as the mosque of Gazi Hassan Pasha. According to another testimony, there was a tradition that the mosque was an old Christian church that was dedicated to Saint Paraskevi.
It is a two-storey building of cubic shape, with an octagonal dome supported by twelve arches. It is built of carved porphyry stones, larger in size on the ground floor and in the lower parts and smaller in the upper floor, placed according to the isodomic system. In the perimeter, large iron-barred windows with arched upper ends pierce the masonry. The north side, which seems to have undergone more recent phases of construction, has a different look. It has six windows, placed under an arch in pairs, which, however, do not end in an arch like those on the other sides, and a tall cornice, which surrounds the narthex on three sides.
In the upper floor, the square prayer hall can be found, which communicates through two doors with the narrow and long narthex to the north. The latter is reached by two built-in staircases located on the east and west sides, respectively. The eastern staircase, the top of which is covered by a two-aisled vaulted propylon, was intended for the entry of officials into the mosque. On the north side of the main hall is the elevated wooden women’s room. On the south side is the mihrab and next to it the minber.
The ground floor is divided into several small spaces, each of which has its own exit, around the monument. These spaces would initially have been used as storage or auxiliaries, while ever since the 20th century, some of them have been operating as shops.
On the west side of the monument the minaret rises, which has a single balcony with a parapet, while a little further is the marble octagonal fountain, which is covered with a vaulted building supported by six arches and low columns.
Due to the great earthquakes that hit Kos during the years 1926 and 1933, the monument was severely damaged. The Italians, under whose occupation the island of Kos was at that time, carried out extensive restoration operations, which included the dismantling of the upper part of the minaret and its restoration. However, due to extensive damages and the structural problems presented, the minaret had to be restored again in 2004-2005. Specifically, after the upper part was dismantled and the worn elements were replaced, it was rebuilt. Nowadays the Mosque is in a relatively good condition. Apart from the restoration undertaken by the Italians, no further major restorative projects have been done. From time to time worn wooden elements are replaced, such as windows and doors, parts of the floor, as well as repairs to the interior plastering and repainting and fixing of the dome.
Nowadays, the mosque operates as a place of worship whereas the ground floor houses commercial venues.
Hatzivasiliou 1990, 419-422