This study is carried out on the settings of Holocene at eastern Gulf of ̇Izmit, Adapazari, Sakarya Delta and its vicinity, and based on 86 samples collected from the boreholes. The pollen diagram, based on the data from the boreholes drilled at Adapazari and its vicinity, suggested that high herbaceous pollen percentages of particularly Chenopodiaceae and Compositae, and Pinus and Quercus were present during the Early Holocene (approximately 11.300 BP years). Absent of the foraminifers in deltaik environment indicates that there was no any sea effect on the delta. In addition, the Gulf of Izmit, which was connected to Sakarya River in the Middle Pleistocene, moved to west. Moreover, when the elevations of the boreholes and different numerical ages (11.000-3.780 BP years) assigned at different depths are considered, it can be concluded that the region was under the control of tectonic activities in the forms of subsidence and uplift.