This study systematically investigated the effects of NbC, TaC, and (Ta,Nb)C additives on the microstructure, mechanical properties, and tribological properties of WC-based composites. The specimens with different additive contents were prepared via ball milling, pressing, and sintering, and were subsequently characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), hardness testing, friction and wear experiments. The results demonstrated that all additives refined WC grains, with NbC exhibiting the most pronounced refinement (a 31.3% reduction in grain size at 0.8   wt.%). In terms of mechanical properties, TaC and (Ta,Nb)C enhanced hardness but significantly reduced fracture toughness, whereas NbC improved hardness with a slower decline in toughness at 0.8   wt.%. Wear tests revealed that the wear rate decreased from 1.05×10 -5 to 8.96×10 -6 mm 3/(N·m) as the NbC content increased from 0 to 0.8   wt.%. The composite (Ta,Nb)C additive exhibited weaker synergistic effects compared to the individual additives. The mechanisms for improving wear resistance involved grain refinement and hardness enhancement, providing theoretical guidance for the design of cemented carbides under extreme conditions.