To elucidate the complex mechanism of solid-solution strengthening in high-entropy alloys (HEAs), it is necessary to determine the effective atomic radii of the constituent elements that are the sources of lattice strain. In the present study, the effective atomic radii of the constituent elements in CrMnFeCoNi HEA that are the basis of the atomic displacements, are evaluated from lattice parameters experimentally determined via θ–2θ X-ray diffraction measurements. The order of the evaluated atomic radii in the present study is different from that of the atomic radii determined via ab-initio calculations in previous studies. The results of the ab-initio calculations indicate a correlation between the yield stress of and the average atomic displacement in the HEA. However, no definite correlation is confirmed by the experimental results in the present study. [ABSTRACT FROM AUTHOR]