Uranium (U), the naturally occurring toxic radionuclide is soluble in aquatic environment as uranyl ion(UO₂²⁺) and hence bioavailable U can affect living organisms adversely. Detection of U in aqueous sam-ples was made simple, cost effective and sensitive by synthesizing a highly specific diglycolamide-capped CdS/ZnS core-shell quantum dot (QD) nanosensor. Its ultratrace level determination was done by conju-gating this nanosensor with cloud point extraction (CPE) procedure. In solution the UO₂²⁺ion gets bondedto the diglycolamide group of the QD nanosensor and a direct Föster Resonance Energy Transfer (FRET)mechanism takes place between the UO₂²⁺ion and QD. This results in increase of the QD fluorescenceintensity and the phenomenon was used to detect the metal ion concentration. The dynamic linear range(DLR) of the method was found to be 1.0–100 ng mL⁻¹ of U in water. The limit of detection (LOD) wasfound to be 0.03 ng mL⁻¹. The developed methodology was validated by measuring the value of U in NISTSRM 1640a which was found to be in agreement with the reported value at 95% confidence level. Themethod was successfully applied to the U determination in three natural water samples with ≤5% ofrelative standard deviation (RSD, 1σ).