<p>Arsenic and its compounds are known to be carcinogenic, mutagenic and teratogenic in nature. Arsenic contamination, particularly As (III), in drinking water has adverse effects on human health. In the present study a simple, rapid, cost effective, eco-friendly and sensitive spectrophotometric method has been developed for the determination of arsenite [As (III)]. The method is based on the reaction of arsenite with a slight excess of N-bromosuccinimide (NBS) and the unconsumed NBS is subsequently determined by the decolourization of Rhodamine-B dye at 555&#xa0;nm, from which the amount of consumed NBS is obtained. The amount of consumed NBS reflects the concentration of arsenite. The effects of various experimental parameters including pH, time, temperature, amounts of oxidant and dye were studied and optimized. Beer’s law was found to obey in the range 0.05–1.0&#xa0;µg mL^‒1. The molar absorptivity and Sandell’s sensitivity were found to be 3.0529 × 10⁴ L mol^‒1 cm^‒1 and 4.075 × 10^‒4 μg cm^‒2, respectively. The method exhibited a detection limit of 0.0028 μg mL^‒1 and a limit of quantification of 0.0087 μg mL^‒1. The method was successfully applied for the determination of As (III) in tap water, ground water, river water, pond water and steel plant discharge water samples.</p> Graphical abstract <p></p>