<p>A new class of materials—high-entropy alloys—is characterized by the presence of atoms with different properties in the absence of a dominant element. In accordance with the self-organization law, this should give rise to new relationships that are unique to high-entropy alloys. The high hardness of high-entropy alloys prompted research into their properties in coatings. The hardness of high-entropy metallic coatings reaches nearly 20 GPa. The mechanical properties of as-cast high-entropy alloys are influenced by lattice distortion (resulting from differences in the atomic radii of elements) and lattice parameter. The relationship between the lattice parameter and distortion and the elastic modulus, hardness, and normalized hardness of high-entropy alloys was analyzed in both as-cast alloys and metallic coatings. The dependence of the elastic modulus and hardness on the lattice parameter was established for as-cast alloys and associated coatings. Coatings with a bcc phase exhibit a slight decrease in the lattice parameter compared with the as-cast state. This is accompanied by a proportional increase in the elastic modulus. At the same time, the elastic modulus of fcc-phase coatings approaches the value found with the rule of mixture as the lattice parameter decreases to the calculated value. The absence of a proportional relationship between the hardness and distortion in as-cast alloys and metallic coatings was demonstrated. The effect of distortion on the normalized hardness (the ratio of hardness to effective elastic modulus) was identified for as-cast alloys. Increasing distortion was found to decrease the hardness ratio between the coating and the as-cast alloy. This is likely associated with the influence of distortion on the nanograin size in the deposition process.</p>