The environmental radioactivity of the Lake Manzala, Egypt, has been investigated to determine the level of the natural radioactivity and the radiological impact for the targeted area. Twenty sediment samples were collected from pre-determined locations, which involve deep springs and lakes, particularly samples taken from places receiving sewage pollutants, fertilizers and disinfection materials used in the agricultural area and fish farms. The gamma-emitting nuclides library has been designed to assess the activity concentration for radionuclides belonging to the natural series of uranium and thorium ( 208 Tl, 212 Bi, 212 Pb, 214 Bi, 214 Pb, 226 Ra, 228 Ac, 234 Th, 235 U), and 40 K gamma-line. The measured overall average value of the radionuclides' activity concentration was 15 Bq/kg, while for 40 K was 286 Bq/kg. The true coincidence summing was corrected using the Genie-2000 software, and LabSOCS was used to calculate the total efficiencies. Most of the resulted values are moderated, indicating normal levels compared to the international and worldwide reference values in this regard.