In this study, the effects of Nb doping on the mechanical properties, deformation mechanism, and wear resistance of an Fe49Mn30Co10Cr10C1 interstitial high-entropy alloy (HEA) were studied. Adding 1 at.% Nb resulted in multi-scale NbC particles. The yield strength and elongation remained almost unchanged, and the wear rate was significantly reduced. The precipitation strengthening of nano-NbC particles offsets the decrease in interstitial strengthening. The formation of NbC particles consumed C, reduced the stacking fault energy (SFE) of the alloy, significantly enhanced the transformation-induced plasticity (TRIP) effect, and offsets the deterioration effect of micron-sized NbC particles on plasticity. After adding Nb element, the volume fraction of strain-induced martensitic transformation in the tensile fracture increases from 13.2 % to 30.6 %. The wear mechanism of the two alloys under sliding wear conditions is mainly abrasive wear. Micron-sized NbC blocks the expansion of the groove and protects the matrix. In addition, the Nb-doped high-entropy alloy produced a thicker deformation ultrafine grain layer and a strain-induced phase transition layer below the wear track. The thicker deformation layer and micron-sized NbC particles reduced the wear rate by more than 23.1 %. The rationality of the existing method for calculating the wear rate with the unit load as a parameter was analyzed, and a new method with the unit maximum shear stress as a parameter is proposed.