Abstract <p>The study of chemical and structural heterogeneities in high-entropy alloys is increasingly attracting the attention of researchers. In this work, the demonstration of capabilities of the magnetostructural approaches is carried out using the example of FeCoNi(P)–Zn Fe-rich non-equiatomic high-entropy alloy coatings produced by Al–induced electroless deposition. The macroscopic, local, and surface magnetic anisotropies are studied by ferromagnetic resonance and approach to magnetic saturation. Analysis of magnetic anisotropy constants and correlation lengths in comparison with information on the nanostructure provides an approach to assessing the homogeneity of high-entropy alloys at different scales. For example, for the studied alloys, it was shown that the uniform easy magnetization axis is localized in two directions within a scale close about to the crystallite size.</p>