<p>In this study, NiCuZn ferrites with the composition Ni_0.29Cu_{0.22−<i>x</i>}Zn_{0.49+<i>x</i>}Fe₂O₄ (<i>x</i> = 0.00–0.10, with a step of 0.02) were synthesized via the solid-state reaction method. Since Zn²⁺ and Cu²⁺ ions occupy different lattice sites in the spinel structure, the influence of the Zn²⁺/Cu²⁺ ratio on the microstructure and microwave magnetic properties was systematically investigated using x-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, vector network analyzer, and ferromagnetic resonance linewidth measurements. All samples exhibited a single-phase spinel structure without secondary phases. As <i>x</i> increased, the grain size decreased from 2.86&#xa0;μm to 1.65&#xa0;μm, the saturation magnetization (4<i>πM</i>_s) exhibited a decreasing trend, and the real part of the permeability (<i>μ′</i>) increased gradually. The ferromagnetic resonance linewidth (<i>Δ</i><i>H</i>) reached a minimum of 119.06&#xa0;Oe at <i>x</i> = 0.06. The effects of Zn²⁺ and Cu²⁺ ions on the microstructure, permeability, and ferromagnetic resonance linewidth were investigated, and the underlying magnetic mechanisms are discussed in detail. The composition Ni_0.29Cu_0.16Zn_0.55Fe₂O₄ (<i>x</i> = 0.06) exhibits excellent properties, with 4<i>πM</i>_s = 4051.67&#xa0;Gs, <i>μ′</i> = 128.6, and <i>Δ</i><i>H</i> = 119.06&#xa0;Oe, showing great potential for application in microwave frequency devices such as phase shifters.</p>