<p>In this study, the effects of Mn concentration and mechanical milling time on the microstructural, magnetic and Mössbauer properties of two FeNiMnCrSi alloys, labeled S1 and S2, were systematically investigated. The alloys were subjected to ball milling for 20, 40, and 80 h, and particle size variation was determined using SEM and zetasizer analyses. Results revealed significant grain refinement, with particle sizes decreasing from the micrometer to the nanometer scale. Zeta potential measurements indicated changes in surface charge characteristics and colloidal stability over time. Magnetization measurements under an external magnetic field varying up to 20 kOe demonstrated that the S1 alloy possessed significantly higher saturation magnetization and coercivity as compared to the S2 alloy. The decrease in magnetization in the S2 alloy was attributed to the higher Mn content. Also, saturation magnetization, remanent magnetization and coercivity decreased with increasing milling time in the both alloys. Mössbauer spectra obtained after 20 h milling revealed the presence of ferromagnetic phases in the S1 alloy, while both ferromagnetic and paramagnetic structures occur in the S2 alloy. As the milling time increased, the ferromagnetic structure turned into paramagnetic doublet structures. This was attributed to the oxidation of particles during milling process. The doublet structure obtained at 40 and 80 h milling was thought to be due to Fe²⁺ and Fe³⁺ ions in the alloy systems.</p>