Abstract: Cu-Nb alloys with relatively high Nb contents (15%, 20%, and 25wt%) were prepared by mechanical alloying combined with spark plasma sintering. The effects of Nb content on the microstructure, mechanical properties, and electrical conductivity of the alloys were systematically investigated and analyzed using scanning electron microscopy, X-ray diffraction, tensile testing, Vickers hardness testing, and four-point probe electrical measurements. The results indicate that partial dissolution of Nb in the Cu matrix occurred in the powder milled for 40 h, and the amount of undissolved Nb increased with increasing Nb content. After sintering, the Nb that had previously dissolved in the Cu matrix precipitated as submicron-scale dispersed particles, exerting a significant influence on the alloy properties. Both the tensile strength and Vickers hardness increased with increasing Nb content, reaching maximum values of 785 MPa and 235.6 HV, respectively, at 25 wt% Nb. The electrical conductivity decreased progressively with increasing Nb content, and the highest value of 59.3 %IACS was obtained at 15 wt%Nb.