<p>Ni₃Fe/ZnFe₂O₄/NiFe₂O₄ nanocomposites were synthesized via high-energy mechanical milling to explore the influence of milling duration on their structural and magnetic properties. A comprehensive characterization was conducted using X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy-dispersive X-ray spectroscopy (EDS), and vibrating sample magnetometry. XRD analysis confirmed the formation of Ni₃Fe, ZnFe₂O₄ and NiFe₂O₄ phases with a body-centred cubic (bcc) and spinel crystal structure, evolving with increased milling time. Crystallite size decreased from 42.82 nm (1 h) to 16.98 nm (30 h), while lattice strain increased from 0.279 to 0.784%, indicating structural refinement and defect accumulation. SEM and EDS analyses revealed morphological homogenization and elemental distribution consistent with the formation of nanocomposites. Magnetic measurements revealed a strong dependence on milling time. Saturation magnetization (<i>M</i>_s) reached a maximum of 59.7 emu g^–1 after 1 h of milling and decreased to 30.96 emu g^–1 at 30 h due to particle size reduction, spin disorder and phase evolution. In contrast, coercivity (<i>H</i>_c), remanent magnetization (<i>M</i>_r) and squareness ratio (<i>M</i>_r/<i>M</i>_s) increased with milling time, reflecting enhanced magnetic anisotropy and domain wall pinning. These findings demonstrate the critical role of mechanical processing in tuning the structural and magnetic behaviour of Ni₃Fe-based nanocomposites, making them promising candidates for applications in electromagnetic devices, magnetic sensors and soft magnetic components.</p>