© 2020, Turkish Chemical Society. All rights reserved.Radionuclides that cause radioactive pollution descend to the bottom in marine and water environments such as heavy metals and accumulate in bottom sediments. It is useful to determine the radionuclides in these environments to control the radionuclide release and its damage. Radioactive pollution can harm people’s life directly or through the food chain. In this study, natural and artificial radionuclide values were measured in Recent sediment samples taken from the seabed in the western part of the Marmara Sea. Gamma spectrometry method was used in radionuclide examinations. In gamma spectrometry studies of sediments, values of radionuclides (40K,137Cs,226Ra,54Mn,95Z, and232Th) were determined. Sea depths where 18 analyzed seafloor sediments are taken vary between 15-50 m. The determined radionuclide concentration activity values of the study area are137Cs (0.9-9.4 (Bq / kg)),232Th (18.9-86 (Bq / kg)),226Ra (10-50 (Bq / kg)),40K (24.4-670 (Bq / kg)),54Mn (0.71-0.9 (Bq / kg)) and95Zr (0.18-0.19 (Bq / kg)). These values were correlated with the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR). The226Ra series,232Th series, and 40K radionuclides accumulate naturally, and their concentrations increase gradually due to anthropogenic impurities.226Ra values obtained across the study areas are within normal limits according to UNSCEAR values.40K and232Th values were higher than UNSCEAR values in all locations. 137 Cs (0.9-9.4 (Bq / kg)) from almost all locations reveals a risky situation in terms of ambient conditions because this element cannot be found in the natural environment and can be found artificially as an end of radioactivity.