A necessary evaluation of freshwater ecosystem pollution levels and radiation risks remains crucial for maintaining environmental health, especially within economically developing areas. This study presents a comprehensive evaluation of the mineralogical, geochemical, and radiological characteristics of sediments in Nasser Lake, Egypt, to determine potential ecological and health risks. Forty sediment samples were collected from multiple locations, including both surface and bottom sediments, for analysis of textural attributes, mineral composition, potentially toxic elements, and natural radionuclides (²³⁸U, ²³²Th, and ⁴⁰K). Results revealed sand-dominated sediments with low organic matter content. The heavy mineral assemblages derived from Nile River inputs, wind-deposited materials, and eroded igneous and metamorphic rocks. Geochemical analysis showed that arsenic, cadmium, chromium, and lead concentrations exceeded upper continental crust background values, with enrichment factors and geo-accumulation indices indicating significant anthropogenic contributions. The pollution indices revealed heavy contamination levels and extreme ecological risks, which were primarily driven by arsenic and cadmium concentrations. Radiological assessments detected activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K below the world average, with hazard indices indicating minimal radiological risk except where localized hotspots were present. The study emphasizes the need for targeted monitoring and sustainable management practices to mitigate pollution and preserve the crucial freshwater environment of Nasser Lake.