A method for the selective and sensitive detection of aluminium (Al3+) in aqueous systems has been devel-oped. The detection is achieved by the selective aggregation of ascorbic acid capped gold nanoparticles(AA-AuNPs) in the presence of aluminium which is observed by the change in colour of the colloidalsolution from bright red to purple. The change in characteristic absorption peak can also be noticedspectrophotometrically; absorption of AA-AuNPs (λmax–520 nm) decreased and a second peak at 652 nmappeared after the addition of aluminium. The ratio of A652/A520 can be used to quantify the concentra-tion of aluminium in water. The method gave a linear response from 20 ppb − 100 ppb (R2= 0.996) of Al3+ in drinking water with a detection limit of 6.5 ppb. The proposed method did not suffer any interferencefrom concomitant transition metal ions like: Mn2+, Ni2+, Zn2+, Sn2+, Li+, Co2+, Hg2+, Fe3+, and Pb2+up toa concentration of 5 ppm and anions (Cl−, F−, SO42−, NO3−, PO43−) up to a concentration of 250 ppm.However, a concentration of Ca2+(≥15 ppm) was found to interfere with the detection of Al3+in groundwater. The interference was eliminated by passing the water through an anion exchange resin convertedinto oxalate form for the removal of the interferant as calcium oxalate precipitate in the resin phase. Afterthis pre-treatment the linearity range in ground water was found to be 100–350 ppb with R2= 0.996 and LOD − 12.5 ppb. The simplicity and rapidity of the developed method shows great potential in favourof its application for screening of drinking water samples to check its safety with respect to aluminiumtoxicity.