This research study focuses on the microstructural, nanocrystalline formation, and magnetic behavior of the Co49Fe21Ti8Nb4B18 nanostructured alloy prepared by mechanical alloying. The structural and magnetic properties of the alloy were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), differential thermal analysis (DTA), and vibrating sample magnetometry (VSM). SEM and TEM analysis revealed that with increasing milling time, the particles became more spherical, more uniform (homogeneous), and the particle size distribution became narrower. The clear and non-overlapping rings observed in the TEM analysis are indicative of solid solution formation. The XRD results showed that as the milling time increased, the intensity of the peaks decreased. After 48 h of milling, the peaks related to titanium and niobium elements disappeared, suggesting the dissolution of these elements into the cobalt-iron crystal lattice, leading to the formation of a solid solution. By increasing the milling time up to 90 h, the grain size reached a minimum of 21.5 nm and slightly increased after 120 h. The strain exhibited an almost increasing trend, reaching a maximum value of 0.472% at 90 h of milling. The shift of the iron-cobalt peak to higher angles in the final stages indicates a contraction of the lattice parameter due to the formation of the solid solution. The saturation magnetization generally showed an increasing trend, reaching 141.3 emu/g at 120 h of milling. The coercivity value did not exhibit a clear trend, but its lowest value was 81.39 Oe at 48 h of milling, and it increased to 101.07 Oe at the end of the milling process. Heat treatment was performed on the sample milled for 120 h, at temperatures of 433°C, 617°C, and 719°C. For all three temperatures, the grain size showed an increasing trend, reaching the highest value of 58.8 nm at 719°C. Compared to the unheated sample, the saturation magnetization inc