It is produced a comprehensive study of corrosion resistance in an aqueous environment and under high-temperature oxidation of copper-based composite materials with NbC dopants (up to 6.22% wt.), which are fabricated by evaporation from two separate crucibles of copper and carbide in a vacuum with subsequent condensation of the mixed vapour stream on a steel substrate. By the method of gravimetric analysis, it is found that the addition of NbC over 1% wt. has a positive effect on increasing the corrosion resistance of the copper-based material in the distilled and tap waters; however, increasing its amount to 6.22% wt. leads to the formation of a more fine-grained structure of the composite material due to a decrease in the rate of recrystallization processes that negatively affects the mechanical properties of the material. The data of chemical analysis of corrosive environments after corrosion tests show high corrosion resistance of Cu–NbC materials. Samples with 1.36–6.22% NbC suffer minor corrosion damage in the static test mode, but in the dynamic mode at 6.22% wt. NbC, the concentration of ions in the corrosion environments increases significantly, probably, due to an increase in the brittleness of the material. At high-temperature oxidation at 370–700°C, the addition of 1.36–6.22% wt. NbC reduces the corrosion rate by half and increases the temperature of the beginning of oxidation by 10–20°C compared to pure condensed copper. Electrochemical studies using the method of removing anodic and cathodic polarization curves show that, in the region of low potential values, the anodic process is described by the Tafel dependence. The addition of niobium carbide to the copper matrix leads to an increase in the overvoltage of the anodic reaction, while the angles of inclination of the straight lines are preserved that confirms the assumption about the protective effect of the NbC-dispersed phase located along the boundaries of the copper grains.