In this study, 7 archaeological ceramics samples, which brought from the Yenikapı res-cue excavations in the Marmaray metro station construction area carried out by the Istanbul Archeology Museums, were examined. ATR-FTIR spectroscopy technique was applied to de-termine the firing temperatures and conditions of the ceramic samples on the settlement, which has yielded findings from the Neolithic Period to the Byzantine and Turkish periods. ATR-FTIR spectra of the samples were taken in the wavelength range of 1800-400 cm-1. The mineralogical composition and firing temperatures of all ceramic samples belonging to Yeni-kapı were successfully determined by using the 2nd order derivative spectra (2nd level poly-nomal degree and 11th level Savitzky-Golay smoothing point). According to the results ob-tained; it was observed that most of the studied ceramic samples were produced from a slight-ly calcareous smectitic clay and consisted mainly of meta-smectite, quartz, calcite and gyp-sum. In addition, different proportions of recarbonated-calcite, meta-kaolinite, diopside, Al-OH, illite, MnO2, magnetite, anorthite, orthoclase and hematite were also detected. It was determined that most of the studied ceramic samples have been fired between 600-800oC in a slightly oxidizing air environment due to the presence of meta-smectite, Al-OH, anorthite, orthoclase and hematite / magnetite minerals.