In this paper, we report the preparation of nanostructured (Ni50Fe50)(100-x)Si-x and (Ni80Fe20)(100-x)Si-x powders prepared by the mechanical alloying method. Elemental maps using scanning electron microscopy as well as X-ray diffraction results showed that iron and silicon dissolved in the nickel lattice homogeneously and formed a face-centered cubic gamma-(Ni (Fe-Si)) uniform solid solution after milling for 24 h. By increasing Si content up to 20 at.%, estimated crystallite sizes for Ni50Fe50 and Ni80Fe20 alloys were reduced from similar to 35 and 46 nm to similar to 9 and 17 nm, respectively. Up to 5 at.% Si, microstrain decreased due to dynamic and static recovery which were prevailing mechanisms due to high work hardening rate of powders. By increasing the Si content, saturation magnetization decreased and different rates of grain refinement resulted in dissimilar behavior of coercivity for two compositions. The maximum saturation magnetization (similar to 156 emu/g) and minimum coercivity (similar to 10 Oe) were achieved for the Ni50Fe50 and (Ni50Fe50)(80)Si-20 alloys, respectively. Crown Copyright (C) 2012 The Society of Powder Technology Japan. Published by Elsevier B.V. All rights reserved.