Several Pt–Ag catalysts supported on activated carbon powder were tested in the catalytic reduction of nitrates in a continuous flow reactor. The influence of the noble metal precursor (Pt(NH3)4(NO3)2 or H2PtCl6), the Pt/Ag atomic ratio (0.3, 1.1 and 1.8) and the metal loading (3% or 1% Pt) were studied. The samples were characterized by XRD, TPR, HRTEM, XPS, H2-chemisorption and nitrogen physisorption. The results showed that the most important variables affecting the catalytic activity are the noble metal precursor and the metal loading, whereas the Pt/Ag atomic ratio does not affect significantly the catalytic behavior. The use of H2PtCl6 instead of Pt(NH3)4(NO3)2 as noble metal precursor leads to more active catalysts. The nitrate conversion is enhanced by the high metal loading (3%).