Changes in various physical properties due to both addition of Ag and substitution of Ag for Cu in the N‐type superconductor system Nd‐Ce‐Cu‐O were investigated by measurements of electrical resistivity, magnetization, X‐ray powder diffraction, X‐ray photoelectron spectroscopy (XPS) and UV photoelectron spectroscopy (UPS). There is only a small decrease in the superconducting transition temperature with Ag dopants up to 40% (compared with Cu). The normal‐state resistivity decreases with the addition of Ag; however, it increases with the substitution of Ag for Cu. The M‐H hysteresis loops at 5 K were enhanced for the 20% Ag‐doped samples. The superconductivity in the Ag‐doped Nd‐Ce‐Cu‐O samples depends greatly on the reduction processing conditions.