Abstract <p>The mechanical properties (nanohardness, Young’s modulus, microhardness, wear resistance), microstructure, and phase composition of the high-entropy alloys Сo₂₀Cr₂₀Fe₁₀Mn₃₀Ni₂₀ and Co₂₀Cr₂₀Zr₉Mn₃₁Ni₂₀ were investigated. The influence of substituting Zr for Fe on the structural-phase state of the CoCrMnNi system was evaluated. In the Co₂₀Cr₂₀Zr₉Mn₃₁Ni₂₀ alloy, intermetallic compounds (e.g., ZrCo₂, Cr₂Ni₃) were observed to form, which may be attributed to the larger atomic radius of Zr (0.160 nm) compared to Co, Cr, Mn, and Ni (~0.125–0.135 nm). This elemental partitioning induces localized lattice strain, promoting elemental segregation and intermetallic formation. The microstructure of the Co₂₀Cr₂₀Fe₁₀Mn₃₀Ni₂₀ and Co₂₀Cr₂₀Zr₉Mn₃₁Ni₂₀ alloys was analyzed via scanning electron microscopy (SEM) combined with characteristic X-ray emission mapping. SEM revealed that substituting zirconium for iron in the high-entropy alloy (up to 10 at %) led to the precipitation of secondary zirconium-rich phases, which reduced the chromium content available for dissolution in the matrix. The Co₂₀Cr₂₀Zr₉Mn₃₁Ni₂₀ alloy exhibited 159% higher nanohardness and a 30.4% greater Young’s modulus compared to the non-equiatomic Cantor high-entropy alloy (CoCrFeMnNi), indicating superior strength and resistance to elastic deformation. The lower margin of error in the Young’s modulus of the Co₂₀Cr₂₀Fe₁₀Mn₃₀Ni₂₀ alloy may stem from its more homogeneous elemental distribution within the as-cast ingot. Both alloys demonstrated comparable wear resistance parameters, with a wear rate of ≈2.08 × 10^–5 g/rev, implying a mass loss of 0.0000208 g per revolution under frictional conditions. This exceptionally low wear rate underscores the need for further investigation into the underlying wear mechanisms.</p>