A couple of fully-dense boron carbide–silicon carbide composites were fabricated by spark-plasma sintering (SPS) from boron carbide + silicon powders, one superhard (i.e., ~28.7(8) GPa) with more than enoguh silicon carbide by SPS of boron carbide + 20vol.% silicon at 1400°C and the other ultrahard (i.e., ~35.1(4) GPa) with little silicon carbide by SPS of boron carbide + 4.28vol.% silicon at 1800°C, and their unlubricated sliding wear was examined and weighted with those of the reference boron carbide monoliths. It was discovered that the two boron-silicon carbide composites endured mild tribo-oxidative wear with preferential removal of the oxide tribolayer, with the one SPS-ed at 1400°C from boron carbide + 20vol.% silicon being, despite its lower hardness and greater proneness to form oxide tribolayer, only slightly less wear resistant than the one SPS-ed at 1800°C from boron carbide + 4.28vol.% silicon (i.e., ~1.0(5)·107 vs 1.37(8)·107 (N·m)/mm³). The reference boron carbide monolith SPS-ed at 1400°C is comparatively two fold less wear resistant (i.e., ~1.70(6)·105 (N·m)/mm³), attributable to its undergoing severe purely mechanical wear by microfracture-dominated three-body abrasion due to its very poor sintering (i.e., high porosity of ~33.5%), poor grain cohesion, and low hardness (i.e., ~3.1(5) GPa). The reference boron carbide monolithc SPS-ed at 1800°C, while equally or less hard (i.e., 28.4(9) GPa) and slightly porous (i.e., ~5.3%), is somewhat more wear resistant (~1.8(3)·107 (N·m)/mm³) than the boron-silicon carbide composites, attributable to its undergoing only mild purely mechanical wear by plasticity dominated two body abrasion without porosity-induced grain pull-out, but it requires SPS temperatures well above 1400°C.