The study details the synthesis of quercetin-capped Au-Ag bimetallic nanoparticles (Qct-AuAg BMNps) in an aqueous environment.UV visible spectra showed absorbance peak of gold and bimetallic nanoparticles at 524 nm and 403 nm, resp.The SEM anal. of Qct-AuAg BMNps showed an average particle size of 67.5 nm with good uniformity (PdI: 0.386).FTIR confirmed the presence of resp. functional groups in Qct-AuAg BMNps.The Qct-AuAg BMNps were used as a colorimetric sensor for detecting calcium dobesilate monohydrate (CDM) in aqueous solutions, showing a linear spectrophotometric relationship with CDM concentration ranging from 0.000001 mM to 10 mM (R2 = 0.9984).The detection and quantification limits were 1.66 x 10-6 and 2.71 x 10-5 mM, resp.The binding constant (Ka) was 9.8 x 104 M-1, with a 1:1 stoichiometry confirmed by Job's plot.The Qct-AuAg BMNps were successfully used to detect CDM in tap water and serum samples.The synthesis process was optimized using Box Behnken Design, with the optimal conditions found at 50°C, 2 mM quercetin, and a 5:1 silver-to-gold ratio.Therefore, the synthesized quercetin capped gold silver bimetallic nanoparticles were proved effective for the detection of CDM in liquid samples.