The effect of the Ni/Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi_(5–x)Cu_x series was studied. The value of temperature of phase transition(T_(ph)) estimated from temperature dependence of electrical resistance varied non-linearly across copper doping from 32.5 K(x=0.0) to 29.1 K(x=5.0). The value of residual resistivity(ρ_o) estimated at low temperature range decreased from 27.28 μΩcm(x=0.0) to 9.44 μΩcm(x=5.0), which was discussed as the influence of microstructure. In order to describe the temperature dependence of resistivity ρ(T) a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges. The change within ρ(T) curvature was evidenced at low temperature range across copper doping. The temperature variation of the resistivity was quite peculiar for Cu-rich compounds(x=4.8, x=5.0), which might be correlated with the incommensurate magnetic structure derived from the weakly negative interaction between the nearest neighbours of Gd. The correlation between microstructure and resistivity was observed. The effect of the Ni / Cu substitution on the electrical resistivity and microstructure of the polycrystalline GdNi_ (5-x) Cu_x series was studied. The value of temperature of phase transition (T_ (ph)) estimated from temperature dependence of electrical resistance varied non -linearly across copper doping from 32.5 K (x = 0.0) to 29.1 K (x = 5.0). The value of residual resistivity (ρ_o) estimated at low temperature range decreased from 27.28 μΩcm 5.0), which was discussed as the influence of microstructure. In order to describe the influence of resistivity ρ (T) a variety of approaches were applied due to different scattering mechanisms occurring at high and low temperature ranges. ) curvature was evidenced at low temperature range across copper doping. The temperature variation of the resistivity was quite peculiar for Cu-rich compounds (x = 4.8, x = 5.0), which might be correlated with the incommensurate magnetic structure derived from th e weakly negative interaction between the nearest neighbors of Gd. The correlation between microstructure and resistivity was observed.