This paper presents the study of the electrochemical deposition of Cu/Sn alloy nanoparticles on Boron Doped Diamond (BDD) films in order to improve their electrocatalytic activity and selectivity for application in nitrate electrochemical reduction. Cyclic voltammetry measurements evidenced the formation of Cu/Sn alloy electrodeposited on BDD electrode. The electrodeposited Cu/Sn can be better visualized by analyzing the dissolution process. By studying the dissolution peak separately, the dissolution peak of the Sn was obtained at a more positive potential, when compared with the dissolution peak of Cu. From the scanning electronic microscopy (SEM) analysis, the homogeneous distribution of the Cu/Sn alloys particles on BDD surface with grain size in nanometric scale was verified. From X-ray diffraction analysis, two Cu/Sn alloy phases (Cu41Sn11 and Cu10Sn3) were identified for the electrodeposits obtained at -0.5V and charge of 0.26 C. The electrocatalytic reduction of nitrate in 0.1 M Britton-Robinson (BR) buffer solution with pH 9 was analyzed. The BDD electrode modified with Cu/Sn alloy nanoparticles proved to potentiate the electrocatalytic reduction of nitrate.