Cyanide (CN−) is known to be a very harmful ion that may accumulate in the air, soil and water, and become a critical risk to organisms, even at trace levels. Hence, it is very critical to develop sensitive and accurate analytical methods for the determination of this anion. In this study, a highly sensitive and simple approach was developed for the quantitative determination of cyanide by UV-Vis spectrophotometry with the aid of synthesized silver nanoparticles (AgNPs) solutions. AgNPs are promising probes frequently used in the determination of both organic and inorganic pollutants. The AgNPs were prepared by reducing silver nitrate (AgNO3) with sodium borohydride (NaBH4) in the presence of Triton X-100 as a stabilizer. The UV-Vis absorption spectra showed that the interaction between cyanide ions and AgNPs made significant decreases in the absorption peak of the surface plasmon resonance (SPR) band at 405 nm. The developed colorimetric sensor exhibited exceptional sensing towards cyanide ions with good linearity in the range of 0.5 and 3.5 mM. The limit of detection (LOD) and the limit of quantification (LOQ) were estimated as 0.09 and 0.29 mM, respectively. Moreover, the proposed colorimetric method was successfully applied to different water samples.