CuAg nanoparticles (CuAgNPs) were electrochemically formed in situ on preanodized, screen-printed carbon electrodes (SPCEs) that possessed many oxygencontaining functional groups capable of adsorbing metal ions, namely Cu 2+ and Ag + . Pre-anodization was achieved using continuous cyclic voltammetry in the range of potential 0.3-2.0 V under a scan rate of 50 mV/s. Cu 2+ and Ag + ions were adsorbed on the pre-anodized SPCE by immersing the electrode in solutions containing both metal ions, and then CuAgNPs were formed in situ via electrochemical reduction in a deaerated, neat NaClO 4 solution after the electrode was ultrasonicated to remove physically adsorbed metal ions. Although CuNPs showed higher activity than AgNPs toward both nitrate (NO 3 − ) and nitrite (NO 2 − ) ions, the instability of CuNPs hindered the application, so CuAgNPs were employed to achieve a compromise between sensitivity and stability. The SPCE/anodized/ CuAgNP electrodes showed activity toward the electrochemical reduction of NO 3 − and NO 2 − , respectively, with the limit of detection (LOD) of 15.6 μM (0.97 ppm) and 11.