The electrochemical behavior of ascorbic acid (AA) and dopamine (DA) at copper nanoparticles modifed polycrystalline gold electrode (nano-Cu/Au) has been studied using cyclic voltammetry. The modifed nano-Cu/Au electrodes have been assembled using cyclic voltammetric techniques. Nano-Cu/Au have been successfully differentiated the electrochemical response of the two species, in contrary to the bare polycrystalline gold electrode at which the electrochemical response of the two species were overlapped, and only one anodic peak for the two species is obtained. At the optimized conditions, both species have been simultaneously determined using square wave voltammetry. Acceptable rectilinear ranges for both species have been obtained with correlation coeffcients of 0.998 and 0.995 for DA and AA, respectively. The limits of detection and quantifcation (LOD and LOQ) were calculated and found to be 1.816 and 6.05 for DA and 34.57 and 115.25 for AA. The relative standard deviation (RSD) for both DA and AA were deliberated to be 2.04 and 0.376 %, respectively